Variable pixel density display system with mechanically-actuated image projector

ABSTRACT

Head-mounted virtual and augmented reality display systems include a light projector with one or more emissive micro-displays having a first resolution and a pixel pitch. The projector outputs light forming frames of virtual content having at least a portion associated with a second resolution greater than the first resolution. The projector outputs light forming a first subframe of the rendered frame at the first resolution, and parts of the projector are shifted using actuators, such that physical positions of light output for individual pixels occupy gaps between the old locations of light output for individual pixels. The projector then outputs light forming a second subframe of the rendered frame. The first and second subframes are outputted within the flicker fusion threshold. Advantageously, an emissive micro-display (e.g., micro-LED display) having a low resolution can form a frame having a higher resolution by using the same light emitters to function as multiple pixels of that frame.

PRIORITY CLAIM

This application is a continuation of U.S. patent application Ser. No.17/418,729, filed Jun. 25, 2021, which is a 371 of International PatentApplication No. PCT/US2019/067816 filed on Dec. 20, 2019, which claimspriority from: U.S. Provisional Application No. 62/911,018 filed on Oct.4, 2019 and titled “AUGMENTED AND VIRTUAL REALITY DISPLAY SYSTEMS WITHSHARED DISPLAY FOR LEFT AND RIGHT EYES”; U.S. Provisional ApplicationNo. 62/800,363 filed on Feb. 1, 2019 and titled “VIRTUAL AND AUGMENTEDREALITY DISPLAY SYSTEMS WITH EMISSIVE MICRO-DISPLAYS”; and U.S.Provisional Application No. 62/786,199 filed on Dec. 28, 2018 and titled“LOW MOTION-TO-PHOTON LATENCY ARCHITECTURE FOR AUGMENTED AND VIRTUALREALITY DISPLAY SYSTEMS”. The above-noted applications are herebyincorporated by reference herein in their entireties.

INCORPORATION BY REFERENCE

This application incorporates by reference the entireties of each of thefollowing: U.S. application Ser. No. 14/555,585 filed on Nov. 27, 2014,published on Jul. 23, 2015 as U.S. Publication No. 2015/0205126; U.S.application Ser. No. 14/690,401 filed on Apr. 18, 2015, published onOct. 22, 2015 as U.S. Publication No. 2015/0302652; U.S. applicationSer. No. 14/212,961 filed on Mar. 14, 2014, now U.S. Pat. No. 9,417,452issued on Aug. 16, 2016; U.S. application Ser. No. 14/331,218 filed onJul. 14, 2014, published on Oct. 29, 2015 as U.S. Publication No.2015/0309263; U.S. Patent App. Pub. No. 2018/0061121, published Mar. 1,2018; U.S. patent application Ser. No. 16/221,065, filed Dec. 14, 2018;U.S. Patent App. Pub. No. 2018/0275410, published Sep. 27, 2018; U.S.Provisional Application No. 62/786,199, filed Dec. 28, 2018; and U.S.application Ser. No. 16/221,359, filed on Dec. 14, 2018; U.S.Provisional Application No. 62/702,707, filed on Jul. 24, 2018; U.S.application Ser. No. 15/481,255, filed Apr. 6, 2017; and U.S.application Ser. No. 15/927,808, filed Apr. 21, 2018, published on Sep.27, 2018 as U.S. Patent App. Pub. No. 2018/0275410.

BACKGROUND Field

The present disclosure relates to display systems and, moreparticularly, to augmented and virtual reality display systems.

Description of the Related Art

Modern computing and display technologies have facilitated thedevelopment of systems for so called “virtual reality” or “augmentedreality” experiences, in which digitally reproduced images or portionsthereof are presented to a user in a manner wherein they seem to be, ormay be perceived as, real. A virtual reality, or “VR”, scenariotypically involves the presentation of digital or virtual imageinformation without transparency to other actual real-world visualinput; an augmented reality, or “AR”, scenario typically involvespresentation of digital or virtual image information as an augmentationto visualization of the actual world around the user. A mixed reality,or “MR”, scenario is a type of AR scenario and typically involvesvirtual objects that are integrated into, and responsive to, the naturalworld. For example, an MR scenario may include AR image content thatappears to be blocked by or is otherwise perceived to interact withobjects in the real world.

Referring to FIG. 1 , an AR scene 10 is depicted. The user of an ARtechnology sees a real-world park-like setting 20 featuring people,trees, buildings in the background, and a concrete platform 30. The useralso perceives that he/she “sees” “virtual content” such as a robotstatue 40 standing upon the real-world platform 30, and a flyingcartoon-like avatar character 50 which seems to be a personification ofa bumble bee. These elements 50, 40 are “virtual” in that they do notexist in the real world. Because the human visual perception system iscomplex, it is challenging to produce AR technology that facilitates acomfortable, natural-feeling, rich presentation of virtual imageelements amongst other virtual or real-world imagery elements.

SUMMARY

According to some embodiments, a head-mounted display system comprises asupport structure configured to mount on a user's head, a lightprojection system supported by the support structure, an eyepiece, andone or more processors. The light projection system comprises amicro-display comprising an array of light emitters associated with afirst resolution, wherein the array of light emitters is configured tooutput light forming frames of virtual content; projection optics; andone or more actuators. The eyepiece is supported by the supportstructure and configured to receive light from the light projectionsystem and to direct the received light to the user, one or moreprocessors. The one or more processors are configured to receive arendered frame of virtual content, the rendered frame comprising atleast a portion associated with a second resolution, wherein the secondresolution is higher than the first resolution. The one or moreprocessors are further configured to cause the emissive micro-displayprojector to output light forming a first subframe of the renderedframe, wherein the first subframe and the rendered frame aresubstantially a same size. The one or more processors are furtherconfigured to shift, via the one or more actuators, one or move parts ofthe light projection system to adjust positions associated with lightemitter light outputted from the light projection system and cause thelight projection system to output light forming a second subframe of therendered frame.

According to some other embodiments, a method implemented by ahead-mounted display system of one or more processors comprisesproviding a rendered frame of virtual content, the rendered framecomprising at least a portion associated with a second resolution. Anemissive micro-display projector is caused to output light forming afirst subframe of the rendered frame, the first subframe having a firstresolution less than the second resolution, wherein the emissivemicro-display projector comprises an array of light emitters associatedwith the first resolution and having a pixel pitch. The emissivemicro-display projector is shifted, via one or more actuators, to adjustgeometric positions associated with light output by the emissivemicro-display projector, wherein the geometric positions are adjusted adistance less than the pixel pitch. The emissive micro-display projectoris caused to output light forming a second subframe of the renderedframe, the second subframe having the first resolution.

According to yet other embodiments, a system comprises one or moreprocessors and one or more computer storage media storing instructionsthat, when executed by the one or more processors, cause the one or moreprocessors to perform operations. The operations comprise generating arendered frame of virtual content to be displayed as augmented realitycontent via an emissive micro-display projector system of the system,the rendered frame being associated with a second resolution, and theemissive micro-display projector comprising one or more light emitterarrays configured to output light forming virtual content associatedwith a first, lower, resolution. The rendered frame of virtual contentis divided into a plurality of subframes, wherein each subframe includesa subset of pixels included in the rendered frame. Light is successivelyoutput via the emissive micro-display projector system, the lightforming the plurality of subframes, wherein the emissive micro-displayprojector system is shifted via one or more actuators for each of thesubframes according to a movement pattern, wherein the emissivemicro-display projector system is shifted along one or more axes on aplane parallel to a plane of an output pupil of the projector system.

According to some other embodiments, a method implemented by ahead-mounted display system of one or more processors comprisesgenerating a rendered frame of virtual content to be displayed asvirtual content via an emissive micro-display projector system of thehead-mounted display system, the rendered frame being associated with asecond resolution, and the emissive micro-display projector comprisingemitters configured to output light forming virtual content associatedwith a first, lower, resolution. The rendered frame of virtual contentis divided into a plurality of subframes, wherein each subframe includesa subset of pixels included in the rendered frame. Light is successivelyoutput via the emissive micro-display projector system, the lightforming the plurality of subframes, wherein the emissive micro-displayprojector system is shifted along one or more axes via one or moreactuators for each of the subframes according to a movement pattern,wherein the emissive micro-display projector system is shifted along oneor more axes on a plane parallel to a plane of an output pupil of theprojector system.

Some additional examples are provided below.

Example 1. A head-mounted display system comprising: a support structureconfigured to mount on a user's head; a light projection systemsupported by the support structure and comprising: a micro-displaycomprising an array of light emitters associated with a firstresolution, wherein the array of light emitters is configured to outputlight forming frames of virtual content; projection optics; and one ormore actuators; an eyepiece supported by the support structure andconfigured to receive light from the light projection system and todirect the received light to the user; and one or more processors, theone or more processors configured to: receive a rendered frame ofvirtual content, the rendered frame comprising at least a portionassociated with a second resolution, wherein the second resolution ishigher than the first resolution; cause the emissive micro-displayprojector to output light forming a first subframe of the renderedframe, wherein the first subframe and the rendered frame aresubstantially a same size; shift, via the one or more actuators, one ormove parts of the light projection system to adjust positions associatedwith light emitter light outputted from the light projection system; andcause the light projection system to output light forming a secondsubframe of the rendered frame.

Example 2. The head-mounted display of example 1, wherein the portionassociated with the second resolution is associated with a foveal regionof a user's eye.

Example 3. The head-mounted display of example 2, wherein the one ormore processors are configured to determine that light forming theportion falls within a threshold angular distance of a fovea of theuser.

Example 4. The head-mounted display of example 2, wherein the one ormore processors are configured to cause: for the second subframe, lightemitters to update emitted light forming the portion; and for the firstsubframe, light emitters to not update emitted light forming parts ofthe rendered frame outside of the portion.

Example 5. The head-mounted display system of example 1, wherein eachemissive micro-display array has an associated emitter size, wherein theemitter size is less than the pixel pitch.

Example 6. The head-mounted display of example 5, wherein a total numberof subframes of the rendered frame is determined based on a sizeassociated with the pixel pitch and the emitter size.

Example 7. The head-mounted display of example 6, wherein the one ormore processors are configured to cause the light projection system tosuccessively output light forming the total number of subframes.

Example 8. The head-mounted display of example 7, wherein the one ormore processors are configured to time multiplex the rendered frame bycausing the one or more actuators to shift parts of the light projectionsystem for each subframe.

Example 9. The head-mounted display of example 8, wherein the one ormore processors are configured to cause the one or more actuators toshift the parts of the light projection system such that geometricpositions associated with the array of light emitters are tiled withinrespective inter-emitter regions.

Example 10. The head-mounted display of example 1, wherein the one ormore processors are configured to cause the one or more actuators toshift the parts of the light projection system according to a movementpattern, and wherein the movement pattern is a continual movementpattern.

Example 11. The head-mounted display of example 1, wherein the firstsubframe and the second subframe each comprise pixels associated withrespective portions of the rendered frame.

Example 12. The head-mounted display of example 1, wherein the lightprojection system comprises a plurality of arrays of light emitters.

Example 13. The head-mounted display of example 12, further comprisingan X-cube prism, wherein each of the arrays of light emitters face adifferent side of the X-cube prism.

Example 14. The head-mounted display of example 12, wherein each of thearrays of light emitters is configured to direct light into dedicatedassociated projection optics.

Example 15. The head-mounted display of example 12, wherein the arraysof light emitters are attached to a common back plane.

Example 16. The head-mounted display of example 1, wherein the one ormore actuators are configured to shift the projection optics.

Example 17. The head-mounted display of example 1, wherein the one ormore actuators are piezoelectric motors.

Example 18. The head-mounted display of example 1, wherein the one ormore actuators shift the emissive micro-display projector along twoaxes.

Example 19. The head-mounted display of example 1, wherein the lightemitters comprise light emitting diodes.

Example 20. The head-mounted display of example 1, wherein the array oflight emitters is configured to emit light of a plurality of componentcolors.

Example 21. The head-mounted display of example 20, wherein each lightemitter comprises a stack of constituent light generators, wherein eachconstituent light generator emits light of a different color.

Example 22. The head-mounted display of example 1, wherein the eyepiececomprises a waveguide assembly comprising one or more waveguides, eachwaveguide comprising: an in-coupling optical element configured toincouple light from the micro-display into the waveguide; and anout-coupling optical element configured to outcouple incoupled light outof the waveguide.

Example 23. A method implemented by a head-mounted display system of oneor more processors, the method comprising: providing a rendered frame ofvirtual content, the rendered frame comprising at least a portionassociated with a second resolution; causing an emissive micro-displayprojector to output light forming a first subframe of the renderedframe, the first subframe having a first resolution less than the secondresolution, wherein the emissive micro-display projector comprises anarray of light emitters associated with the first resolution and havinga pixel pitch; shifting, via one or more actuators, the emissivemicro-display projector to adjust geometric positions associated withlight output by the emissive micro-display projector, wherein thegeometric positions are adjusted a distance less than the pixel pitch;and causing the emissive micro-display projector to output light forminga second subframe of the rendered frame, the second subframe having thefirst resolution.

Example 24. A system comprising: one or more processors; and one or morecomputer storage media storing instructions that, when executed by theone or more processors, cause the one or more processors to performoperations comprising: generating a rendered frame of virtual content tobe displayed as augmented reality content via an emissive micro-displayprojector system of the system, the rendered frame being associated witha second resolution, and the emissive micro-display projector comprisingone or more light emitter arrays configured to output light formingvirtual content associated with a first, lower, resolution; dividing therendered frame of virtual content into a plurality of subframes, whereineach subframe includes a subset of pixels included in the renderedframe; and successively outputting light via the emissive micro-displayprojector system, the light forming the plurality of subframes, whereinthe emissive micro-display projector system is shifted via one or moreactuators for each of the subframes according to a movement pattern,wherein the emissive micro-display projector system is shifted along oneor more axes on a plane parallel to a plane of an output pupil of theprojector system.

Example 25. The system of example 24, wherein the one or more processorsare configured to cause the one or more actuators to shift the emissivemicro-display projector such that geometric positions associated withthe emissive micro-display arrays are tiled within respectiveinter-emitter regions.

Example 26. The system of example 25, wherein the one or more processorsare configured to cause the one or more actuators to shift the lightemitter arrays along the one or axes.

Example 27. The system of example 25, wherein the micro-displayprojector system comprises projection optics, wherein the one or moreprocessors are configured to cause the one or more actuators to shiftthe projection optics along the one or more axes, the projection opticsbeing configured to output light to a user of the system.

Example 28. A method implemented by a head-mounted display system of oneor more processors, the method comprising: generating a rendered frameof virtual content to be displayed as virtual content via an emissivemicro-display projector system of the head-mounted display system, therendered frame being associated with a second resolution, and theemissive micro-display projector comprising emitters configured tooutput light forming virtual content associated with a first, lower,resolution; dividing the rendered frame of virtual content into aplurality of subframes, wherein each subframe includes a subset ofpixels included in the rendered frame; and successively outputting lightvia the emissive micro-display projector system, the light forming theplurality of subframes, wherein the emissive micro-display projectorsystem is shifted along one or more axes via one or more actuators foreach of the subframes according to a movement pattern, wherein theemissive micro-display projector system is shifted along one or moreaxes on a plane parallel to a plane of an output pupil of the projectorsystem.

Example 28. The method of example 28, wherein the emissive micro-displayprojector system is shifted such that geometric positions associatedwith light emitter arrays are tiled within respective inter-emitterregions.

Example 29. The method of example 29, wherein the one or more actuatorsshift the light emitter arrays along the one or axes.

Example 30. The method of example 29, wherein the one or more actuatorsshift projection optics of the micro-LED projector system along the oneor more axes, the projection optics being configured to output light toa user of the head-mounted display system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a user's view of augmented reality (AR) through an ARdevice.

FIG. 2 illustrates a conventional display system for simulatingthree-dimensional imagery for a user.

FIGS. 3A-3C illustrate relationships between radius of curvature andfocal radius.

FIG. 4A illustrates a representation of the accommodation-vergenceresponse of the human visual system.

FIG. 4B illustrates examples of different accommodative states andvergence states of a pair of eyes of the user.

FIG. 4C illustrates an example of a representation of a top-down view ofa user viewing content via a display system.

FIG. 4D illustrates another example of a representation of a top-downview of a user viewing content via a display system.

FIG. 5 illustrates aspects of an approach for simulatingthree-dimensional imagery by modifying wavefront divergence.

FIG. 6 illustrates an example of a waveguide stack for outputting imageinformation to a user.

FIG. 7 illustrates an example of exit beams outputted by a waveguide.

FIG. 8 illustrates an example of a stacked eyepiece in which each depthplane includes images formed using multiple different component colors.

FIG. 9A illustrates a cross-sectional side view of an example of a setof stacked waveguides that each includes an in-coupling optical element.

FIG. 9B illustrates a perspective view of an example of the plurality ofstacked waveguides of FIG. 9A.

FIG. 9C illustrates a top-down plan view of an example of the pluralityof stacked waveguides of FIGS. 9A and 9B.

FIG. 9D illustrates a top-down plan view of another example of aplurality of stacked waveguides.

FIG. 9E illustrates an example of wearable display system.

FIG. 10 illustrates an example of a wearable display system with a lightprojection system having a spatial light modulator and a separate lightsource.

FIG. 11A illustrates an example of a wearable display system with alight projection system having multiple emissive micro-displays.

FIG. 11B illustrates an example of an emissive micro-display with anarray of light emitters.

FIG. 12 illustrates another example of a wearable display system with alight projection system having multiple emissive micro-displays andassociated light redirecting structures.

FIG. 13A illustrates an example of a side-view of a wearable displaysystem with a light projection system having multiple emissivemicro-displays and an eyepiece having waveguides with overlapping andlaterally-shifted light in-coupling optical elements.

FIG. 13B illustrates another example of a wearable display system with alight projection system having multiple emissive micro-displaysconfigured to direct light to a single light in-coupling area of aneyepiece.

FIG. 14 illustrates an example of a wearable display system with asingle emissive micro-display.

FIG. 15 illustrates a side view of an example of an eyepiece having astack of waveguides with overlapping in-coupling optical elements.

FIG. 16 illustrates a side view of an example of a stack of waveguideswith color filters for mitigating ghosting or crosstalk betweenwaveguides.

FIG. 17 illustrates an example of a top-down view of the eyepieces ofFIGS. 15 and 16 .

FIG. 18 illustrates another example of a top-down view of the eyepiecesof FIGS. 15 and 16 .

FIG. 19A illustrates a side view of an example of an eyepiece having astack of waveguides with overlapping and laterally-shifted in-couplingoptical elements.

FIG. 19B illustrates a side view of an example of the eyepiece of FIG.19A with color filters for mitigating ghosting or crosstalk betweenwaveguides.

FIG. 20A illustrates an example of a top-down view of the eyepieces ofFIGS. 19A and 19B.

FIG. 20B illustrates another example of a top-down view of the eyepiecesof FIGS. 19A and 19B.

FIG. 21 illustrates a side view of an example of re-bounce in awaveguide.

FIGS. 22A-22C illustrate examples of top-down views of an eyepiecehaving in-coupling optical elements configured to reduce re-bounce.

FIGS. 23A-23C illustrate additional examples of top-down views of aneyepiece having in-coupling optical elements configured to reducere-bounce.

FIG. 24A illustrates an example of angular emission profiles of lightemitted by individual light emitters of an emissive micro-display, andlight captured by projection optics.

FIG. 24B illustrates an example of the narrowing of angular emissionprofiles using an array of light collimators.

FIG. 25A illustrates an example of a side view of an array of taperedreflective wells for directing light to projection optics.

FIG. 25B illustrates an example of a side view of an asymmetric taperedreflective well.

FIGS. 26A-26C illustrate examples of differences in light paths forlight emitters at different positions relative to center lines ofoverlying lens.

FIG. 27 illustrates an example of a side view of individual lightemitters of an emissive micro-display with an overlying nano-lens array.

FIG. 28 is a perspective view of an example of the emissivemicro-display of FIG. 27 .

FIG. 29 illustrates an example of a wearable display system with thefull-color emissive micro-display of FIG. 28 .

FIG. 30A illustrates an example of a wearable display system with anemissive micro-display and an associated array of light collimators.

FIG. 30B illustrates an example of a light projection system withmultiple emissive micro-displays, each with an associated array of lightcollimators.

FIG. 30C illustrates an example of a wearable display system withmultiple emissive micro-displays, each with an associated array of lightcollimators.

FIGS. 31A and 31B illustrate examples of waveguide assemblies havingvariable focus elements for varying the wavefront divergence of light toa viewer.

FIG. 32A illustrates an example of an emissive micro-display having anarray of light emitters that are separated by gaps.

FIG. 32B illustrates an example of how the emissive micro-display ofFIG. 32A may be configured to emulate a higher fill-factor micro-displayvia time-multiplexing and repositioning of the array or associatedoptics.

FIG. 32C illustrates an example of a foveated image formed by anemissive micro-display, such as the emissive micro-display of FIG. 32A.

FIG. 32D illustrates an example of an emissive micro-display, such asthe emissive micro-display of FIG. 32A, configured to form foveatedimages with three or more levels of resolution within the image.

FIG. 33 illustrates another example of a foveated image provided by anemissive micro-display, such as the emissive micro-display of FIG. 32A.

FIG. 34 illustrates various example paths of movement of parts of anemissive micro-display to shift the positions of displayed pixels.

FIGS. 35A and 35B illustrate how displacement of light emitters andprojection optics may change the position of a displayed pixel.

FIG. 36A illustrates an example of a wearable display system having alight projection system with an actuator coupled to projection optics.

FIG. 36B illustrates an example of a wearable display system having alight projection system with multiple actuators, each coupled to adifferent micro-display.

FIG. 37A illustrates an example of a wearable display system having alight projection system with an eyepiece having a single waveguide.

FIG. 37B illustrates an example of a wearable display system having alight projection system in which a single array of light emittersoutputs light of different component colors with an actuator coupled toprojection optics.

FIG. 37C illustrates an example of a wearable display system similar tothe wearable display system of FIG. 37B, except for attachment of theactuator to a micro-display rather than the projection optics.

FIG. 38A illustrates an example of a wearable display system having alight projection system that directs light of different component colorsto an eyepiece without using an optical combiner to combine light ofdifferent colors with an actuator coupled to projection optics.

FIG. 38B illustrates another example of a wearable display system havinga light projection system that directs light of different componentcolors to an eyepiece without using an optical combiner to combine thelight of different colors with an actuator coupled to projection optics.

FIG. 38C illustrates an example of a wearable display system similar tothe wearable display system of FIG. 38A, except for attachment ofactuators to individual micro-displays rather than the projectionoptics.

FIG. 38D illustrates an example of a wearable display system similar tothe wearable display system of FIG. 38B, except for attachment of theactuator to an integral micro-display structure rather than theprojection optics.

FIG. 39 illustrates a flowchart of an example process for outputtingsubframes of a rendered frame of virtual content.

DETAILED DESCRIPTION

Augmented reality (AR) or virtual reality (VR) systems may displayvirtual content to a user, or viewer. This content may be displayed on ahead-mounted display, for example, as part of eyewear, that projectsimage information to the user's eyes. In addition, where the system isan AR system, the display may also transmit light from a surroundingenvironment to the user's eyes, to allow a view of the surroundingenvironment. As used herein, it will be appreciated that a“head-mounted” or “head mountable” display is a display that may bemounted on the head of the user or viewer.

To improve the usability of AR or VR systems (also referred to simply as“display systems”), it may be beneficial to reduce the size, weight,and/or power consumption of the display systems. As an example, a usermay be more likely to utilize a display system if the size, and generalobtrusiveness, of the display system is decreased. As another example, auser may be more likely to utilize a display system if the weight placedon the user's head is reduced. Similarly, reduced power consumption canallow the use of smaller batteries, reduce heat generated by the displaysystem, and so on. Various embodiments described herein facilitate suchbenefits, including reductions in the size of parts of display systems.

As described herein, light forming virtual content (also referred toherein as image light) may be generated by one or more displaytechnologies. For example, the light may be generated by a lightprojection system included in a display system. This light may then berouted via optics for output as virtual content to a user of the displaysystem. The virtual content may be represented as image pixels includedin rendered frames successively presented to the user. To achievehigh-quality (e.g., lifelike) virtual content, the display system mayrender, and then output, frames of virtual content at a sufficientresolution (e.g., greater than a threshold resolution). Accordingly, theimage pixels may be sufficiently close together to achieve thesufficient resolution.

However, it will be appreciated that design constraints associated witha display system may limit the ability to achieve such closeness inimage pixels, and thus resolution. For example, to miniaturize a displaysystem, the display system may be required to have a reduced displaysize (e.g., a projector size). An example display may include a liquidcrystal on silicon (LCoS) display. To output image light forming virtualcontent, the LCoS display may be required to utilize a separateillumination module including one or more light emitters. In thisexample, an LCoS panel may impose spatially varying modulation on thegenerated light to form virtual content. However, to decrease a sizeassociated with an LCoS panel while preserving a high resolution, thepixel pitch associated with the LCoS panel may need to be reduced. Pixelpitch, as described herein, may represent a physical distance on adisplay between similar locations on similar elements of the displayforming image pixels. Due to physical constraints regarding small pixelpitches, coupled with the necessity of a separate illumination module,an LCoS display may be larger than desired in some applications.

Some embodiments disclosed herein advantageously include an emissivemicro-display, such as a micro-LED display. In some embodiments, themicro-displays are micro-OLED displays. Display systems utilizing anemissive micro-display may avoid the added bulk of an illuminationmodule. Additionally, an emissive micro-display may facilitate thepresentation of images with an apparent advantageously small pixelpitch. As described, an example display system may utilize one or morean emissive micro-displays to achieve reduced size, weight, powerconsumption, among other benefits.

Emissive micro-displays have several advantages for use in wearabledisplay systems. As an example, the power consumption of emissivemicro-displays generally varies with image content, such that dim orsparse content requires less power to display. Since AR environments mayoften be sparse—since it may generally be desirable for the user to beable to see their surrounding environment—emissive micro-displays mayhave an average power consumption below that of other displaytechnologies that use a spatial light modulator to modulate light from alight source. In contrast, other display technologies may utilizesubstantial power even for dim, sparse, or “all off”, virtual content.As another example, emissive micro-displays may offer an exceptionallyhigh frame-rate (which may enable the use of a partial-resolution array)and may provide low levels of visually apparent motion artifacts (e.g.,motion blur). As another example, emissive micro-displays may notrequire polarization optics of the type required by LCoS displays. Thus,emissive micro-displays may avoid the optical losses present inpolarization optics.

While arrays of light emitters, such as micro-LEDs, may provide forsubstantial size, weight, and/or power savings, current light emittersmay not provide for sufficiently small pixel pitch to enable highresolution virtual content in small display system form factors. As anon-limiting example, some micro-LED-based micro-displays may allow fora pixel pitch of about 2 to about 3 micron. Even at such pixel pitches,to provide a desired number of pixels, the micro-LED display may stillbe undesirably large for use in a wearable display system, particularlysince a goal for such systems may be to have a form factor and sizesimilar to that of eyeglasses.

As described in more detail, a light projection system including anemissive micro-display may achieve an effective small pixel pitch viarapid physical adjustment, or displacement, to parts of the lightprojection system. For example, the emissive micro-display may bephysically adjusted in position, or displaced, along one or more axes.As another example, optical elements (e.g., projection optics) may bephysically adjusted in position, or displaced, along one or more axes.

As described herein, a size associated with a light emitter, such as amicro-LED, may be referred to as emitter size. The emitter size mayrefer to a dimension of the light emitter along a particular axis (e.g.,lateral axis). Emitter size may also refer to dimensions of the lightemitter along two axes (e.g., lateral and longitudinal axes). Similarly,pixel pitch may refer to a distance between similar points on directlyadjacent light emitters along a particular axis (e.g., lateral axis),with different axes having their own pixel pitch. For example, in someembodiments, the light emitters may be placed more closely along a firstaxis than along a second axis (e.g., an orthogonal axis). An example ofan array of light emitters is described in more detail herein andillustrated in FIG. 32A.

It will be appreciated that the size of a light emitter may be less thanthe gap that separates directly neighboring light emitters. For example,due to physical and electrical constraints, it may be challenging toform an emissive micro-display with light emitters at greater than athreshold density. Example constraints may include current crowding,substrate droop, and so on. Thus, there may be substantial gaps orspaces between adjacent light emitters. The gap between two lightemitters is referred to herein as an inter-emitter region. Inter-emitterregions, an example of which is illustrated in FIG. 32A, may thereforedelineate an area of an emissive micro-display (e.g., a maximum area)which includes a single light emitter. The size of inter-emitter regionsmay therefore limit the extent to which an emissive micro-display mayachieve certain high densities or high resolutions.

Advantageously, the ability to operate light emitters, such asmicro-LEDs, at high speeds may allow time-multiplexed presentation of animage using the same one or more emissive micro-displays; for example,the geometric position of light emitters relative to projection opticsmay be shifted to allowed the same light emitters to present differentpixels of the image at different times. In some embodiments, a renderedframe of virtual content may be presented as a series of subframes inrapid succession via time-multiplexing schemes. In this example, eachsubframe may be associated with a particular physical position of thelight emitters relative to the projection optics. Thus, it will beappreciated that the geometric position may be varied by changing thelocations of the light emitters and the projection optics relative toone another (e.g., by changing the physical position of light emitterswhile keeping the projection optics stationary, by changing the physicalposition of the projection optics while keeping the light emittersstationary, or by changing the physical positions of both the lightemitters and the projection optics). As described in more detail below,the geometric positions may be adjusted (e.g., via one or moreactuators) to cause the light emitters to tile respective inter-emitterregions. Thus, the emissive micro-display may achieve output ofadvantageously high resolution virtual content.

Thus, a light projection system may be configured to project individualfull-resolution frames of virtual content by projecting one or morepartial-resolution subframes. For example, one or morepartial-resolution subframes may be projected. The subframes may beprojected in rapid succession and may be offset from each-other (e.g.,by a less than a full pixel pitch along one or more axes on which thesubframes are translated). For example, an emissive micro-displayincluded in the projector may be physically displaced along one or moreaxes. As described above, an emissive micro-display may include lightemitters, such as micro-LEDs, having a pixel pitch. This pixel pitch maythus inform a resolution at which the emissive micro-display may outputframes of virtual content. To effectively decrease the functional pixelpitch and gap between light emitters, and thus increase a resolution fora same size display, the light emitters may be adjusted in position, forexample, by less than the pixel pitch. As an example, a display mayinclude light emitters separated by a pixel pitch of 2.5 microns, andeach light emitter may have an emitter size of 0.833 microns. In someembodiments, the light emitters may be adjusted in position a number oftimes based on the number of times that the light emitters may betranslated to different (e.g., non-overlapping) positions within aninter-emitter region. In this example, the inter-emitter region may be6.25 microns², and an example light emitter may be adjusted in positionthree times along a first axis and three times along a second,orthogonal axis. Thus, the example light emitter may effectively assume9 positions within the inter-emitter region. For one or more of the 9positions, a particular subframe of a same rendered frame of virtualcontent may be presented. Thus, the successively presented subframes maybe perceived as a high-resolution frame of virtual content. In effect,the light emitters may form images with a higher apparent pixel densitythan the physical density of the light emitters.

In some embodiments, the visual system of users may merge together thesubframes such that users perceive the full-resolution frames. Forexample, the pixels of the subframes may be interwoven to form afull-resolution frame. Preferably, the subframes may be sequentiallydisplayed at a frame rate higher than the flicker fusion threshold ofthe human visual system. As an example, the flicker fusion threshold maybe 60 Hz, which is considered to be sufficiently fast that most users donot perceive the subframes as being displayed at different times. Insome embodiments, the different subframes are sequentially displayed ata rate equal to or higher than the flicker fusion threshold (e.g., equalto or higher than 60 Hz).

As a result, an emissive micro-display can be configured to have fewerlight emitters than the number of image pixels contained in eachfull-resolution rendered frame of virtual content. For example, afull-resolution image could include 2000×2000 pixels, while the emissivemicro-display may be an array of only 1000×1000 elements. The use oflower-resolution emissive micro-displays can be particularly beneficialfor wearable systems such as the display systems described herein. As anexample, a lower-resolution display may be smaller, weigh less, and/orconsume less power that a higher-resolution display.

While the above has described moving or adjusting the position of anemissive micro-display (including, for example, micro-LED arrays), itwill be appreciated that the position of projection optics mayalternatively, or additionally, be adjusted. For example, and as will bedescribed in more detail below with respect to FIGS. 35A-35B, theprojection optics may route light generated via the emissivemicro-display to a user of a display system. As an example, theprojection optics may route light to input in-coupling optical elements(e.g., in-coupling gratings) of eyepieces configured to receive anddirect light encoded with image information (image light) to the user.Thus, instead of physically translating the emissive micro-display, theprojection optics may be translated along one or more axes. In moving,the projection optics may change a geometric position of each arrayalong one or more axes prior to outputting light for in-coupling via thein-coupling gratings. As described herein, a light projection system mayencompass one or more emissive micro-displays, projection optics, and soon. Thus, the light output of light projection system may be adjusted bythe physical translation of parts of the system (e.g., by changing thelocations of pixels presented by the light projection system).

It will be appreciated that certain portions of a rendered frame ofvirtual content may be more visually apparent to a user than otherportions. For example, the user may have heightened visual acuity forportions of virtual content falling on the user's fovea (herein referredto as “foveal portions”). To determine the locations of these fovealportions, a display system may determine a fixation point at which auser is fixating. Portions of virtual content falling within a thresholdangular distance of this fixation point may be identified as falling ona fovea of the user. As will be described, the display system may beconfigured to increase a resolution associated with foveal portions. Theresolution of remaining portions may be increased less or not increased.

As an example, an emissive micro-display may be configured to updatepixels included in a foveal portion at a greater rate than for pixelsincluded in other portions. As described above, geometric positions oflight emitters may be translated, or adjusted, to tile an inter-emitterregion of the array. Optionally, light emitters utilized to output lightforming pixels including a foveal region may be updated for a relativelyhigh proportion of the different geometric positions (e.g., for eachdifferent geometric position), while light emitters for forming pixelsaway from the foveal region may be updated for a lower proportion of thedifferent geometric positions (e.g., these light emitters may be “off”or may simply present the same information as in a previous position).Light emitters utilized to output light forming pixels included in otherregions may be updated less. For example, these light emitters may beupdated twice, or only once, for a given full-resolution rendered frameof virtual content. For example, the light emitters for a foveal regionmay be updated for each of four different geometric positions withininter-emitter regions, while light emitters corresponding to peripheralparts of an image may be updated only for every other geometricpositions.

As a result, a rendered frame formed from rapidly displayed or projectedsubframes may have an effective resolution which varies across therendered frame. With foveated imaging, the effective resolution of anemissive micro-display can be made high in foveal regions (e.g., regionsof interest, regions in which a user is focused, regions designated by auser, regions designated by a designer, etc.) and can be made lower inother regions (e.g., outside regions of interest). Configuring theemissive micro-displays to provide foveated images may further help toconverse resources, for example by eliminating and/or reducingprocessing and power loads associated with displaying or projectingfewer interesting regions (e.g., regions unlikely to be the focus ofusers' attentions).

Example Display Systems with Emissive Micro-Displays

Advantageously, as noted herein, display systems utilizing emissivemicro-displays as described herein may allow for a low-weight andcompact form factor, and may also provide a high frame rate and lowmotion blur. Preferably, the micro-displays are emissive micro-displays,which provide advantages for high brightness and high pixel density. Insome embodiments, the emissive micro-displays are micro-LED displays. Insome other embodiments, the emissive micro-displays are micro-OLEDdisplays. In some embodiments, the emissive micro-displays comprisearrays of light emitters having a pitch of, e.g., less than 10 μm, lessthan 8 μm, less than 6 μm, less than 5 μm, or less than 2 μm, including1-5 μm, and an emitter size of 2 μm or less, 1.7 μm or less, or 1.3 μmor less. In some embodiments, the emitter size is within a range havingan upper limit of the above-noted sizes and a lower limit of 1 μm. Insome embodiments, the ratio of emitter size to pitch is 1:1 to 1:5, 1:2to 1:4, or 1:2 to 1:3, which may have advantages for individual controlof emitters and efficient utilization of emitted light by eyepieces, asdiscussed further herein.

In some embodiments, a plurality of emissive micro-displays may beutilized to form images for a head-mounted display system. The lightcontaining the image information for forming these images may bereferred to as image light. It will be appreciated that image light mayvary in, e.g., wavelength, intensity, polarization, etc. The emissivemicro-displays output image light to an eyepiece, which then relays thelight to an eye of the user.

In some embodiments, the plurality of emissive micro-displays may beutilized and positioned at different sides of an optical combiner, e.g.,an X-cube prism or dichroic X-cube. The X-cube prism receives light raysfrom different micro-displays on different faces of the cube and outputsthe light rays from the same face of the cube. The outputted light maybe directed towards projection optics, which is configured to convergeor focus the image light onto the eyepiece.

In some embodiments, the plurality of emissive micro-displays comprisesmonochrome micro-displays, which are configured to output light of asingle component color. Combining various component colors forms a fullcolor image. In some other embodiments, one or more of the emissivemicro-displays may have sub-pixels configured to emit light of two ormore, but not all, component colors utilized by the display system. Forexample, a single emissive micro-display may have sub-pixels which emitlight of the colors blue and green, while a separate emissivemicro-display on a different face of the X-cube may have pixelsconfigured to emit red light. In some embodiments, the plurality ofmicro-displays are each full-color displays comprising, e.g., pixelsformed of multiple sub-pixels configured to emit light of differentcomponent colors. Advantageously, combining the light of multiplefull-color micro-displays may increase display brightness and dynamicrange.

It will be appreciated that the emissive micro-displays may comprisearrays of light emitters. The light emitters may emit light with aLambertian angular emission profile. Undesirably, such an angularremission profile may “waste” light, since only a small portion of theemitted light may ultimately be incident on the eyepiece. In someembodiments, light collimators may be utilized to narrow the angularemission profile of light emitted by the light emitters. As used herein,a light collimator is an optical structure which narrows the angularemission profile of incident light; that is, the light collimatorreceives light from an associated light emitter with a relatively wideinitial angular emission profile and outputs that light with a narrowerangular emission profile than the wide initial angular emission profile.In some embodiments, the rays of light exiting the light collimator aremore parallel than the rays of light received by the light collimator,before being transmitted through and exiting the collimator. Examples oflight collimators include micro-lenses, nano-lenses, reflective wells,metasurfaces, and liquid crystal gratings. In some embodiments, thelight collimators may be configured to steer light to ultimatelyconverge on different laterally-shifted light-coupling optical elements.In some embodiments, each light emitter has a dedicated lightcollimator. The light collimators are preferably positioned directlyadjacent or contacting the light emitters, to capture a large proportionof the light emitted by the associated light emitters.

In some embodiments, a single emissive micro-display may be utilized todirect light to the eyepiece. For example, the single emissivemicro-display may be a full-color display comprising light emitters thatemit light of different component colors. In some embodiments, the lightemitters may form groups, which are localized in a common area, witheach group comprising light emitters which emit light of each componentcolor. In such embodiments, each group of light emitters may share acommon micro-lens. Advantageously, light of different colors fromdifferent light emitters take a different path through the micro-lens,which may be manifested in light of different component colors beingincident on different in-coupling optical elements of an eyepiece, asdiscussed herein.

In some embodiments, the full-color micro-display may comprise repeatinggroups of light emitters of the same component color. For instance, themicro-display may include rows of light emitters, with the lightemitters of each individual row configured to emit light of the samecolor. Thus, different rows may emit light of different componentcolors. In addition, the micro-display may have an associated array oflight collimators configured to direct light to a desired location on aneyepiece, e.g., to an associated in-coupling optical element.Advantageously, while the individual light emitters of such a full-colormicro-display may not be positioned to form a high-quality full-colorimage, as viewed directly on the micro-display, the lens arrayappropriately steers the light from the light emitters to the eyepiece,which combines monochrome images formed by light emitters of differentcolors, thereby forming a high-quality full-color image.

In some embodiments, the eyepiece receiving image light from themicro-displays may comprise a waveguide assembly. The area of awaveguide of the waveguide assembly on which the image light is incidentmay include in-coupling optical elements which in-couple incident imagelight, such that the light propagates through the waveguide by totalinternal reflection (TIR). In some embodiments, the waveguide assemblymay include a stack of waveguides, each of which has an associatedin-coupling optical element. Different in-coupling optical elements maybe configured to in-couple light of different colors, such thatdifferent waveguides may be configured to propagate light of differentcolors therein. The waveguides may include out-coupling opticalelements, which out-couple light propagating therein, such that theout-coupled light propagates towards the eye of the user. In some otherembodiments, the waveguide assembly may include a single waveguidehaving an associated in-coupling optical element configured to in-couplelight of different component colors.

In some embodiments, the in-coupling optical elements are laterallyshifted, as seen from the projection optics. Different in-couplingoptical elements may be configured to in-couple light of differentcolors. Preferably, image light of different colors take different pathsto the eyepiece and, thus, impinge upon different correspondingin-coupling optical elements.

In some other embodiments, other types of eyepieces or optics forrelaying image light to the eyes of the user may be utilized. Forexample, as discussed herein, the eyepiece may include one or morewaveguides which propagates image light therein by TIR. As anotherexample, the eyepiece may include a birdbath combiner comprising asemitransparent mirror that both directs image light to a viewer andallows a view of the ambient environment.

In some embodiments, the eyepiece may be configured to selectivelyoutput light with different amounts of wavefront divergence, to providevirtual content at a plurality of virtual depth planes (also referred tosimply as “depth planes” herein) perceived to be at different distancesaway from the user. For example, the eyepiece may comprise a pluralityof waveguides each having out-coupling optical elements with differentoptical power to output light with different amounts of wavefrontdivergence. In some other embodiments, a variable focus element may beprovided between the eyepiece and the user's eye. The variable focuselement may be configured to dynamically change optical power to providethe desired wavefront divergence for particular virtual content. In someembodiments, as an alternative to, or in addition to waveguide opticalstructures for providing optical power, the display systems may alsoinclude a plurality of lenses that provide or additionally provideoptical powers.

In addition to the compact form factor and high frame rates discussedabove, emissive micro-displays according to some embodiments may provideone of more of the following advantages. For example, the micro-displaysmay provide exceptionally small pixel pitches and high pixel density.The micro-displays may also provide high luminance and efficiency. Forexample, the light emitters of the emissive micro-displays may onlyconsume power to emit light when the light emitters are needed providecontent with luminance. This is in contrast to other displaytechnologies in which the light source may illuminate an entire panel ofpixels, whether or not some of those pixels are dark. Further, it willbe appreciated that the human visual system integrates received lightover time and the light emitters of emissive micro-displays, such asmicro-LEDs, have advantageously high duty cycles (e.g., including ashort activation period for a light emitter in a micro-display to risefrom an “off” to a full “on” state, and a correspondingly short time tofall from an “on” state to “off” state allow the light emitters to emitlight at the on level for a large percentage of each cycle). As aresult, the power used to generate an image with a given perceivedbrightness may be less as compared to conventional display technologieswith lower duty cycles. In some embodiments, the duty cycle may be 70%or more, 80% or more, or 90% or more. In some embodiments, the dutycycle may be about 99%. In addition, as noted herein, micro-displays mayfacilitate exceptionally high frame rates, which may provide advantagesincluding reducing mismatches between the position of a user's head andthe displayed content.

Reference will now be made to the drawings, in which like referencenumerals refer to like parts throughout. Unless indicated otherwise, thedrawings are schematic and not necessarily drawn to scale.

FIG. 2 illustrates a conventional display system for simulatingthree-dimensional imagery for a user. It will be appreciated that auser's eyes are spaced apart and that, when looking at a real object inspace, each eye will have a slightly different view of the object andmay form an image of the object at different locations on the retina ofeach eye. This may be referred to as binocular disparity and may beutilized by the human visual system to provide a perception of depth.Conventional display systems simulate binocular disparity by presentingtwo distinct images 190, 200 with slightly different views of the samevirtual object—one for each eye 210, 220—corresponding to the views ofthe virtual object that would be seen by each eye were the virtualobject a real object at a desired depth. These images provide binocularcues that the user's visual system may interpret to derive a perceptionof depth.

With continued reference to FIG. 2 , the images 190, 200 are spaced fromthe eyes 210, 220 by a distance 230 on a z-axis. The z-axis is parallelto the optical axis of the viewer with their eyes fixated on an objectat optical infinity directly ahead of the viewer. The images 190, 200are flat and at a fixed distance from the eyes 210, 220. Based on theslightly different views of a virtual object in the images presented tothe eyes 210, 220, respectively, the eyes may naturally rotate such thatan image of the object falls on corresponding points on the retinas ofeach of the eyes, to maintain single binocular vision. This rotation maycause the lines of sight of each of the eyes 210, 220 to converge onto apoint in space at which the virtual object is perceived to be present.As a result, providing three-dimensional imagery conventionally involvesproviding binocular cues that may manipulate the vergence of the user'seyes 210, 220, and that the human visual system interprets to provide aperception of depth.

Generating a realistic and comfortable perception of depth ischallenging, however. It will be appreciated that light from objects atdifferent distances from the eyes have wavefronts with different amountsof divergence. FIGS. 3A-3C illustrate relationships between distance andthe divergence of light rays. The distance between the object and theeye 210 is represented by, in order of decreasing distance, R1, R2, andR3. As shown in FIGS. 3A-3C, the light rays become more divergent asdistance to the object decreases. Conversely, as distance increases, thelight rays become more collimated. Stated another way, it may be saidthat the light field produced by a point (the object or a part of theobject) has a spherical wavefront curvature, which is a function of howfar away the point is from the eye of the user. The curvature increaseswith decreasing distance between the object and the eye 210. While onlya single eye 210 is illustrated for clarity of illustration in FIGS.3A-3C and other figures herein, the discussions regarding eye 210 may beapplied to both eyes 210 and 220 of a viewer.

With continued reference to FIGS. 3A-3C, light from an object that theviewer's eyes are fixated on may have different degrees of wavefrontdivergence. Due to the different amounts of wavefront divergence, thelight may be focused differently by the lens of the eye, which in turnmay require the lens to assume different shapes to form a focused imageon the retina of the eye. Where a focused image is not formed on theretina, the resulting retinal blur acts as a cue to accommodation thatcauses a change in the shape of the lens of the eye until a focusedimage is formed on the retina. For example, the cue to accommodation maytrigger the ciliary muscles surrounding the lens of the eye to relax orcontract, thereby modulating the force applied to the suspensoryligaments holding the lens, thus causing the shape of the lens of theeye to change until retinal blur of an object of fixation is eliminatedor minimized, thereby forming a focused image of the object of fixationon the retina (e.g., fovea) of the eye. The process by which the lens ofthe eye changes shape may be referred to as accommodation, and the shapeof the lens of the eye required to form a focused image of the object offixation on the retina (e.g., fovea) of the eye may be referred to as anaccommodative state.

With reference now to FIG. 4A, a representation of theaccommodation-vergence response of the human visual system isillustrated. The movement of the eyes to fixate on an object causes theeyes to receive light from the object, with the light forming an imageon each of the retinas of the eyes. The presence of retinal blur in theimage formed on the retina may provide a cue to accommodation, and therelative locations of the image on the retinas may provide a cue tovergence. The cue to accommodation causes accommodation to occur,resulting in the lenses of the eyes each assuming a particularaccommodative state that forms a focused image of the object on theretina (e.g., fovea) of the eye. On the other hand, the cue to vergencecauses vergence movements (rotation of the eyes) to occur such that theimages formed on each retina of each eye are at corresponding retinalpoints that maintain single binocular vision. In these positions, theeyes may be said to have assumed a particular vergence state. Withcontinued reference to FIG. 4A, accommodation may be understood to bethe process by which the eye achieves a particular accommodative state,and vergence may be understood to be the process by which the eyeachieves a particular vergence state. As indicated in FIG. 4A, theaccommodative and vergence states of the eyes may change if the userfixates on another object. For example, the accommodated state maychange if the user fixates on a new object at a different depth on thez-axis.

Without being limited by theory, it is believed that viewers of anobject may perceive the object as being “three-dimensional” due to acombination of vergence and accommodation. As noted above, vergencemovements (e.g., rotation of the eyes so that the pupils move toward oraway from each other to converge the lines of sight of the eyes tofixate upon an object) of the two eyes relative to each other areclosely associated with accommodation of the lenses of the eyes. Undernormal conditions, changing the shapes of the lenses of the eyes tochange focus from one object to another object at a different distancewill automatically cause a matching change in vergence to the samedistance, under a relationship known as the “accommodation-vergencereflex.” Likewise, a change in vergence will trigger a matching changein lens shape under normal conditions.

With reference now to FIG. 4B, examples of different accommodative andvergence states of the eyes are illustrated. The pair of eyes 222 a isfixated on an object at optical infinity, while the pair eyes 222 b arefixated on an object 221 at less than optical infinity. Notably, thevergence states of each pair of eyes is different, with the pair of eyes222 a directed straight ahead, while the pair of eyes 222 converge onthe object 221. The accommodative states of the eyes forming each pairof eyes 222 a and 222 b are also different, as represented by thedifferent shapes of the lenses 210 a, 220 a.

Undesirably, many users of conventional “3-D” display systems find suchconventional systems to be uncomfortable or may not perceive a sense ofdepth at all due to a mismatch between accommodative and vergence statesin these displays. As noted above, many stereoscopic or “3-D” displaysystems display a scene by providing slightly different images to eacheye. Such systems are uncomfortable for many viewers, since they, amongother things, simply provide different presentations of a scene andcause changes in the vergence states of the eyes, but without acorresponding change in the accommodative states of those eyes. Rather,the images are shown by a display at a fixed distance from the eyes,such that the eyes view all the image information at a singleaccommodative state. Such an arrangement works against the“accommodation-vergence reflex” by causing changes in the vergence statewithout a matching change in the accommodative state. This mismatch isbelieved to cause viewer discomfort. Display systems that provide abetter match between accommodation and vergence may form more realisticand comfortable simulations of three-dimensional imagery.

Without being limited by theory, it is believed that the human eyetypically may interpret a finite number of depth planes to provide depthperception. Consequently, a highly believable simulation of perceiveddepth may be achieved by providing, to the eye, different presentationsof an image corresponding to each of these limited numbers of depthplanes. In some embodiments, the different presentations may provideboth cues to vergence and matching cues to accommodation, therebyproviding physiologically correct accommodation-vergence matching.

With continued reference to FIG. 4B, two depth planes 240, correspondingto different distances in space from the eyes 210, 220, are illustrated.For a given depth plane 240, vergence cues may be provided by thedisplaying of images of appropriately different perspectives for eacheye 210, 220. In addition, for a given depth plane 240, light formingthe images provided to each eye 210, 220 may have a wavefront divergencecorresponding to a light field produced by a point at the distance ofthat depth plane 240.

In the illustrated embodiment, the distance, along the z-axis, of thedepth plane 240 containing the point 221 is 1 m. As used herein,distances or depths along the z-axis may be measured with a zero-pointlocated at the exit pupils of the user's eyes. Thus, a depth plane 240located at a depth of 1 m corresponds to a distance of 1 m away from theexit pupils of the user's eyes, on the optical axis of those eyes withthe eyes directed towards optical infinity. As an approximation, thedepth or distance along the z-axis may be measured from the display infront of the user's eyes (e.g., from the surface of a waveguide), plus avalue for the distance between the device and the exit pupils of theuser's eyes. That value may be called the eye relief and corresponds tothe distance between the exit pupil of the user's eye and the displayworn by the user in front of the eye. In practice, the value for the eyerelief may be a normalized value used generally for all viewers. Forexample, the eye relief may be assumed to be 20 mm and a depth planethat is at a depth of 1 m may be at a distance of 980 mm in front of thedisplay.

With reference now to FIGS. 4C and 4D, examples of matchedaccommodation-vergence distances and mismatched accommodation-vergencedistances are illustrated, respectively. As illustrated in FIG. 4C, thedisplay system may provide images of a virtual object to each eye 210,220. The images may cause the eyes 210, 220 to assume a vergence statein which the eyes converge on a point 15 on a depth plane 240. Inaddition, the images may be formed by a light having a wavefrontcurvature corresponding to real objects at that depth plane 240. As aresult, the eyes 210, 220 assume an accommodative state in which theimages are in focus on the retinas of those eyes. Thus, the user mayperceive the virtual object as being at the point 15 on the depth plane240.

It will be appreciated that each of the accommodative and vergencestates of the eyes 210, 220 are associated with a particular distance onthe z-axis. For example, an object at a particular distance from theeyes 210, 220 causes those eyes to assume particular accommodativestates based upon the distances of the object. The distance associatedwith a particular accommodative state may be referred to as theaccommodation distance, A_(d). Similarly, there are particular vergencedistances, V_(d), associated with the eyes in particular vergencestates, or positions relative to one another. Where the accommodationdistance and the vergence distance match, the relationship betweenaccommodation and vergence may be said to be physiologically correct.This is considered to be the most comfortable scenario for a viewer.

In stereoscopic displays, however, the accommodation distance and thevergence distance may not always match. For example, as illustrated inFIG. 4D, images displayed to the eyes 210, 220 may be displayed withwavefront divergence corresponding to depth plane 240, and the eyes 210,220 may assume a particular accommodative state in which the points 15a, 15 b on that depth plane are in focus. However, the images displayedto the eyes 210, 220 may provide cues for vergence that cause the eyes210, 220 to converge on a point 15 that is not located on the depthplane 240. As a result, the accommodation distance corresponds to thedistance from the exit pupils of the eyes 210, 220 to the depth plane240, while the vergence distance corresponds to the larger distance fromthe exit pupils of the eyes 210, 220 to the point 15, in someembodiments. The accommodation distance is different from the vergencedistance. Consequently, there is an accommodation-vergence mismatch.Such a mismatch is considered undesirable and may cause discomfort inthe user. It will be appreciated that the mismatch corresponds todistance (e.g., V_(d)−A_(d)) and may be characterized using diopters.

In some embodiments, it will be appreciated that a reference point otherthan exit pupils of the eyes 210, 220 may be utilized for determiningdistance for determining accommodation-vergence mismatch, so long as thesame reference point is utilized for the accommodation distance and thevergence distance. For example, the distances could be measured from thecornea to the depth plane, from the retina to the depth plane, from theeyepiece (e.g., a waveguide of the display device) to the depth plane,and so on.

Without being limited by theory, it is believed that users may stillperceive accommodation-vergence mismatches of up to about 0.25 diopter,up to about 0.33 diopter, and up to about 0.5 diopter as beingphysiologically correct, without the mismatch itself causing significantdiscomfort. In some embodiments, display systems disclosed herein (e.g.,the display system 250, FIG. 6 ) present images to the viewer havingaccommodation-vergence mismatch of about 0.5 diopter or less. In someother embodiments, the accommodation-vergence mismatch of the imagesprovided by the display system is about 0.33 diopter or less. In yetother embodiments, the accommodation-vergence mismatch of the imagesprovided by the display system is about 0.25 diopter or less, includingabout 0.1 diopter or less.

FIG. 5 illustrates aspects of an approach for simulatingthree-dimensional imagery by modifying wavefront divergence. The displaysystem includes a waveguide 270 that is configured to receive light 770that is encoded with image information, and to output that light to theuser's eye 210. The waveguide 270 may output the light 650 with adefined amount of wavefront divergence corresponding to the wavefrontdivergence of a light field produced by a point on a desired depth plane240. In some embodiments, the same amount of wavefront divergence isprovided for all objects presented on that depth plane. In addition, itwill be illustrated that the other eye of the user may be provided withimage information from a similar waveguide.

In some embodiments, a single waveguide may be configured to outputlight with a set amount of wavefront divergence corresponding to asingle or limited number of depth planes and/or the waveguide may beconfigured to output light of a limited range of wavelengths.Consequently, in some embodiments, a plurality or stack of waveguidesmay be utilized to provide different amounts of wavefront divergence fordifferent depth planes and/or to output light of different ranges ofwavelengths. As used herein, it will be appreciated at a depth plane maybe planar or may follow the contours of a curved surface.

FIG. 6 illustrates an example of a waveguide stack for outputting imageinformation to a user. A display system 250 includes a stack ofwaveguides, or stacked waveguide assembly, 260 that may be utilized toprovide three-dimensional perception to the eye/brain using a pluralityof waveguides 270, 280, 290, 300, 310. It will be appreciated that thedisplay system 250 may be considered a light field display in someembodiments. In addition, the waveguide assembly 260 may also bereferred to as an eyepiece.

In some embodiments, the display system 250 may be configured to providesubstantially continuous cues to vergence and multiple discrete cues toaccommodation. The cues to vergence may be provided by displayingdifferent images to each of the eyes of the user, and the cues toaccommodation may be provided by outputting the light that forms theimages with selectable discrete amounts of wavefront divergence. Statedanother way, the display system 250 may be configured to output lightwith variable levels of wavefront divergence. In some embodiments, eachdiscrete level of wavefront divergence corresponds to a particular depthplane and may be provided by a particular one of the waveguides 270,280, 290, 300, 310.

With continued reference to FIG. 6 , the waveguide assembly 260 may alsoinclude a plurality of features 320, 330, 340, 350 between thewaveguides. In some embodiments, the features 320, 330, 340, 350 may beone or more lenses. The waveguides 270, 280, 290, 300, 310 and/or

the plurality of lenses 320, 330, 340, 350 may be configured to sendimage information to the eye with various levels of wavefront curvatureor light ray divergence. Each waveguide level may be associated with aparticular depth plane and may be configured to output image informationcorresponding to that depth plane. Image injection devices 360, 370,380, 390, 400 may function as a source of light for the waveguides andmay be utilized to inject image information into the waveguides 270,280, 290, 300, 310, each of which may be configured, as describedherein, to distribute incoming light across each respective waveguide,for output toward the eye 210. Light exits an output surface 410, 420,430, 440, 450 of the image injection devices 360, 370, 380, 390, 400 andis injected into a corresponding input surface 460, 470, 480, 490, 500of the waveguides 270, 280, 290, 300, 310. In some embodiments, each ofthe input surfaces 460, 470, 480, 490, 500 may be an edge of acorresponding waveguide, or may be part of a major surface of thecorresponding waveguide (that is, one of the waveguide surfaces directlyfacing the world 510 or the viewer's eye 210). In some embodiments, asingle beam of light (e.g. a collimated beam) may be injected into eachwaveguide to output an entire field of cloned collimated beams that aredirected toward the eye 210 at particular angles (and amounts ofdivergence) corresponding to the depth plane associated with aparticular waveguide. In some embodiments, a single one of the imageinjection devices 360, 370, 380, 390, 400 may be associated with andinject light into a plurality (e.g., three) of the waveguides 270, 280,290, 300, 310.

In some embodiments, the image injection devices 360, 370, 380, 390, 400are discrete displays that each produce image information for injectioninto a corresponding waveguide 270, 280, 290, 300, 310, respectively. Insome other embodiments, the image injection devices 360, 370, 380, 390,400 are the output ends of a single multiplexed display which may, e.g.,pipe image information via one or more optical conduits (such as fiberoptic cables) to each of the image injection devices 360, 370, 380, 390,400. It will be appreciated that the image information provided by theimage injection devices 360, 370, 380, 390, 400 may include light ofdifferent wavelengths, or colors (e.g., different component colors, asdiscussed herein).

In some embodiments, the light injected into the waveguides 270, 280,290, 300, 310 is provided by a light projection system 520, whichcomprises a light module 530, which may include a light emitter, such asa light emitting diode (LED). The light from the light module 530 may bedirected to and modified by a light modulator 540, e.g., a spatial lightmodulator, via a beam splitter 550. The light modulator 540 may beconfigured to change the perceived intensity of the light injected intothe waveguides 270, 280, 290, 300, 310 to encode the light with imageinformation. Examples of spatial light modulators include liquid crystaldisplays (LCD) including a liquid crystal on silicon (LCOS) displays. Insome other embodiments, the spatial light modulator may be a MEMSdevice, such as a digital light processing (DLP) device. It will beappreciated that the image injection devices 360, 370, 380, 390, 400 areillustrated schematically and, in some embodiments, these imageinjection devices may represent different light paths and locations in acommon projection system configured to output light into associated onesof the waveguides 270, 280, 290, 300, 310. In some embodiments, thewaveguides of the waveguide assembly 260 may function as ideal lenswhile relaying light injected into the waveguides out to the user'seyes. In this conception, the object may be the spatial light modulator540 and the image may be the image on the depth plane.

In some embodiments, the display system 250 may be a scanning fiberdisplay comprising one or more scanning fibers configured to projectlight in various patterns (e.g., raster scan, spiral scan, Lissajouspatterns, etc.) into one or more waveguides 270, 280, 290, 300, 310 andultimately to the eye 210 of the viewer. In some embodiments, theillustrated image injection devices 360, 370, 380, 390, 400 mayschematically represent a single scanning fiber or a bundle of scanningfibers configured to inject light into one or a plurality of thewaveguides 270, 280, 290, 300, 310. In some other embodiments, theillustrated image injection devices 360, 370, 380, 390, 400 mayschematically represent a plurality of scanning fibers or a plurality ofbundles of scanning fibers, each of which are configured to inject lightinto an associated one of the waveguides 270, 280, 290, 300, 310. Itwill be appreciated that one or more optical fibers may be configured totransmit light from the light module 530 to the one or more waveguides270, 280, 290, 300, 310. It will be appreciated that one or moreintervening optical structures may be provided between the scanningfiber, or fibers, and the one or more waveguides 270, 280, 290, 300, 310to, e.g., redirect light exiting the scanning fiber into the one or morewaveguides 270, 280, 290, 300, 310.

A controller 560 controls the operation of one or more of the stackedwaveguide assembly 260, including operation of the image injectiondevices 360, 370, 380, 390, 400, the light source 530, and the lightmodulator 540. In some embodiments, the controller 560 is part of thelocal data processing module 140. The controller 560 includesprogramming (e.g., instructions in a non-transitory medium) thatregulates the timing and provision of image information to thewaveguides 270, 280, 290, 300, 310 according to, e.g., any of thevarious schemes disclosed herein. In some embodiments, the controllermay be a single integral device, or a distributed system connected bywired or wireless communication channels. The controller 560 may be partof the processing modules 140 or 150 (FIG. 9E) in some embodiments.

With continued reference to FIG. 6 , the waveguides 270, 280, 290, 300,310 may be configured to propagate light within each respectivewaveguide by total internal reflection (TIR). The waveguides 270, 280,290, 300, 310 may each be planar or have another shape (e.g., curved),with major top and bottom surfaces and edges extending between thosemajor top and bottom surfaces. In the illustrated configuration, thewaveguides 270, 280, 290, 300, 310 may each include out-coupling opticalelements 570, 580, 590, 600, 610 that are configured to extract lightout of a waveguide by redirecting the light, propagating within eachrespective waveguide, out of the waveguide to output image informationto the eye 210. Extracted light may also be referred to as out-coupledlight and the out-coupling optical elements light may also be referredto light extracting optical elements. An extracted beam of light may beoutputted by the waveguide at locations at which the light propagatingin the waveguide strikes a light extracting optical element. Theout-coupling optical elements 570, 580, 590, 600, 610 may, for example,be gratings, including diffractive optical features, as discussedfurther herein. While illustrated disposed at the bottom major surfacesof the waveguides 270, 280, 290, 300, 310, for ease of description anddrawing clarity, in some embodiments, the out-coupling optical elements570, 580, 590, 600, 610 may be disposed at the top and/or bottom majorsurfaces, and/or may be disposed directly in the volume of thewaveguides 270, 280, 290, 300, 310, as discussed further herein. In someembodiments, the out-coupling optical elements 570, 580, 590, 600, 610may be formed in a layer of material that is attached to a transparentsubstrate to form the waveguides 270, 280, 290, 300, 310. In some otherembodiments, the waveguides 270, 280, 290, 300, 310 may be a monolithicpiece of material and the out-coupling optical elements 570, 580, 590,600, 610 may be formed on a surface and/or in the interior of that pieceof material.

With continued reference to FIG. 6 , as discussed herein, each waveguide270, 280, 290, 300, 310 is configured to output light to form an imagecorresponding to a particular depth plane. For example, the waveguide270 nearest the eye may be configured to deliver collimated light (whichwas injected into such waveguide 270), to the eye 210. The collimatedlight may be representative of the optical infinity focal plane. Thenext waveguide up 280 may be configured to send out collimated lightwhich passes through the first lens 350 (e.g., a negative lens) beforeit may reach the eye 210; such first lens 350 may be configured tocreate a slight convex wavefront curvature so that the eye/braininterprets light coming from that next waveguide up 280 as coming from afirst focal plane closer inward toward the eye 210 from opticalinfinity. Similarly, the third up waveguide 290 passes its output lightthrough both the first 350 and second 340 lenses before reaching the eye210; the combined optical power of the first 350 and second 340 lensesmay be configured to create another incremental amount of wavefrontcurvature so that the eye/brain interprets light coming from the thirdwaveguide 290 as coming from a second focal plane that is even closerinward toward the person from optical infinity than was light from thenext waveguide up 280.

The other waveguide layers 300, 310 and lenses 330, 320 are similarlyconfigured, with the highest waveguide 310 in the stack sending itsoutput through all of the lenses between it and the eye for an aggregatefocal power representative of the closest focal plane to the person. Tocompensate for the stack of lenses 320, 330, 340, 350 whenviewing/interpreting light coming from the world 510 on the other sideof the stacked waveguide assembly 260, a compensating lens layer 620 maybe disposed at the top of the stack to compensate for the aggregatepower of the lens stack 320, 330, 340, 350 below. Such a configurationprovides as many perceived focal planes as there are availablewaveguide/lens pairings. Both the out-coupling optical elements of thewaveguides and the focusing aspects of the lenses may be static (i.e.,not dynamic or electro-active). In some alternative embodiments, eitheror both may be dynamic using electro-active features.

In some embodiments, two or more of the waveguides 270, 280, 290, 300,310 may have the same associated depth plane. For example, multiplewaveguides 270, 280, 290, 300, 310 may be configured to output imagesset to the same depth plane, or multiple subsets of the waveguides 270,280, 290, 300, 310 may be configured to output images set to the sameplurality of depth planes, with one set for each depth plane. This mayprovide advantages for forming a tiled image to provide an expandedfield of view at those depth planes.

With continued reference to FIG. 6 , the out-coupling optical elements570, 580, 590, 600, 610 may be configured to both redirect light out oftheir respective waveguides and to output this light with theappropriate amount of divergence or collimation for a particular depthplane associated with the waveguide. As a result, waveguides havingdifferent associated depth planes may have different configurations ofout-coupling optical elements 570, 580, 590, 600, 610, which outputlight with a different amount of divergence depending on the associateddepth plane. In some embodiments, the light extracting optical elements570, 580, 590, 600, 610 may be volumetric or surface features, which maybe configured to output light at specific angles. For example, the lightextracting optical elements 570, 580, 590, 600, 610 may be volumeholograms, surface holograms, and/or diffraction gratings. In someembodiments, the features 320, 330, 340, 350 may not be lenses; rather,they may simply be spacers (e.g., cladding layers and/or structures forforming air gaps).

In some embodiments, the out-coupling optical elements 570, 580, 590,600, 610 are diffractive features that form a diffraction pattern, or“diffractive optical element” (also referred to herein as a “DOE”).Preferably, the DOE's have a sufficiently low diffraction efficiency sothat only a portion of the light of the beam is deflected away towardthe eye 210 with each intersection of the DOE, while the rest continuesto move through a waveguide via TIR. The light carrying the imageinformation is thus divided into a number of related exit beams thatexit the waveguide at a multiplicity of locations and the result is afairly uniform pattern of exit emission toward the eye 210 for thisparticular collimated beam bouncing around within a waveguide.

In some embodiments, one or more DOEs may be switchable between “on”states in which they actively diffract, and “off” states in which theydo not significantly diffract. For instance, a switchable DOE maycomprise a layer of polymer dispersed liquid crystal, in whichmicrodroplets comprise a diffraction pattern in a host medium, and therefractive index of the microdroplets may be switched to substantiallymatch the refractive index of the host material (in which case thepattern does not appreciably diffract incident light) or themicrodroplet may be switched to an index that does not match that of thehost medium (in which case the pattern actively diffracts incidentlight).

In some embodiments, a camera assembly 630 (e.g., a digital camera,including visible light and infrared light cameras) may be provided tocapture images of the eye 210 and/or tissue around the eye 210 to, e.g.,detect user inputs and/or to monitor the physiological state of theuser. As used herein, a camera may be any image capture device. In someembodiments, the camera assembly 630 may include an image capture deviceand a light source to project light (e.g., infrared light) to the eye,which may then be reflected by the eye and detected by the image capturedevice. In some embodiments, the camera assembly 630 may be attached tothe frame or support structure 80 (FIG. 9E) and may be in electricalcommunication with the processing modules 140 and/or 150, which mayprocess image information from the camera assembly 630. In someembodiments, one camera assembly 630 may be utilized for each eye, toseparately monitor each eye.

The camera assembly 630 may, in some embodiments, observe movements ofthe user, such as the user's eye movements. As an example, the cameraassembly 630 may capture images of the eye 210 to determine the size,position, and/or orientation of the pupil of the eye 210 (or some otherstructure of the eye 210). The camera assembly 630 may, if desired,obtain images (processed by processing circuitry of the type describedherein) used to determine the direction the user is looking (e.g., eyepose or gaze direction). In some embodiments, camera assembly 630 mayinclude multiple cameras, at least one of which may be utilized for eacheye, to separately determine the eye pose or gaze direction of each eyeindependently. The camera assembly 630 may, in some embodiments and incombination with processing circuitry such as the controller 560 or thelocal data processing module 140, determine eye pose or gaze directionbased on glints (e.g., reflections) of reflected light (e.g., infraredlight) from a light source included in camera assembly 630.

With reference now to FIG. 7 , an example of exit beams outputted by awaveguide is shown. One waveguide is illustrated, but it will beappreciated that other waveguides in the waveguide assembly 260 (FIG. 6) may function similarly, where the waveguide assembly 260 includesmultiple waveguides. Light 640 is injected into the waveguide 270 at theinput surface 460 of the waveguide 270 and propagates within thewaveguide 270 by TI R. At points where the light 640 impinges on the DOE570, a portion of the light exits the waveguide as exit beams 650. Theexit beams 650 are illustrated as substantially parallel but, asdiscussed herein, they may also be redirected to propagate to the eye210 at an angle (e.g., forming divergent exit beams), depending on thedepth plane associated with the waveguide 270. It will be appreciatedthat substantially parallel exit beams may be indicative of a waveguidewith out-coupling optical elements that out-couple light to form imagesthat appear to be set on a depth plane at a large distance (e.g.,optical infinity) from the eye 210. Other waveguides or other sets ofout-coupling optical elements may output an exit beam pattern that ismore divergent, which would require the eye 210 to accommodate to acloser distance to bring it into focus on the retina and would beinterpreted by the brain as light from a distance closer to the eye 210than optical infinity.

In some embodiments, a full color image may be formed at each depthplane by overlaying images in each of the component colors, e.g., threeor more component colors. FIG. 8 illustrates an example of a stackedwaveguide assembly in which each depth plane includes images formedusing multiple different component colors. The illustrated embodimentshows depth planes 240 a-240 f, although more or fewer depths are alsocontemplated. Each depth plane may have three or more component colorimages associated with it, including: a first image of a first color, G;a second image of a second color, R; and a third image of a third color,B. Different depth planes are indicated in the figure by differentnumbers for diopters (dpt) following the letters G, R, and B. Just asexamples, the numbers following each of these letters indicate diopters(1/m), or inverse distance of the depth plane from a viewer, and eachbox in the figures represents an individual component color image. Insome embodiments, to account for differences in the eye's focusing oflight of different wavelengths, the exact placement of the depth planesfor different component colors may vary. For example, differentcomponent color images for a given depth plane may be placed on depthplanes corresponding to different distances from the user. Such anarrangement may increase visual acuity and user comfort and/or maydecrease chromatic aberrations.

In some embodiments, light of each component color may be outputted by asingle dedicated waveguide and, consequently, each depth plane may havemultiple waveguides associated with it. In such embodiments, each box inthe figures including the letters G, R, or B may be understood torepresent an individual waveguide, and three waveguides may be providedper depth plane where three component color images are provided perdepth plane. While the waveguides associated with each depth plane areshown adjacent to one another in this drawing for ease of description,it will be appreciated that, in a physical device, the waveguides mayall be arranged in a stack with one waveguide per level. In some otherembodiments, multiple component colors may be outputted by the samewaveguide, such that, e.g., only a single waveguide may be provided perdepth plane.

With continued reference to FIG. 8 , in some embodiments, G is the colorgreen, R is the color red, and B is the color blue. In some otherembodiments, other colors associated with other wavelengths of light,including magenta and cyan, may be used in addition to or may replaceone or more of red, green, or blue.

It will be appreciated that references to a given color of lightthroughout this disclosure will be understood to encompass light of oneor more wavelengths within a range of wavelengths of light that areperceived by a viewer as being of that given color. For example, redlight may include light of one or more wavelengths in the range of about620-780 nm, green light may include light of one or more wavelengths inthe range of about 492-577 nm, and blue light may include light of oneor more wavelengths in the range of about 435-493 nm.

In some embodiments, the light source 530 (FIG. 6 ) may be configured toemit light of one or more wavelengths outside the visual perceptionrange of the viewer, for example, infrared and/or ultravioletwavelengths. In addition, the in-coupling, out-coupling, and other lightredirecting structures of the waveguides of the display 250 may beconfigured to direct and emit this light out of the display towards theuser's eye 210, e.g., for imaging and/or user stimulation applications.

With reference now to FIG. 9A, in some embodiments, light impinging on awaveguide may need to be redirected to in-couple that light into thewaveguide. An in-coupling optical element may be used to redirect andin-couple the light into its corresponding waveguide. FIG. 9Aillustrates a cross-sectional side view of an example of a plurality orset 660 of stacked waveguides that each includes an in-coupling opticalelement. The waveguides may each be configured to output light of one ormore different wavelengths, or one or more different ranges ofwavelengths. It will be appreciated that the stack 660 may correspond tothe stack 260 (FIG. 6 ) and the illustrated waveguides of the stack 660may correspond to part of the plurality of waveguides 270, 280, 290,300, 310, except that light from one or more of the image injectiondevices 360, 370, 380, 390, 400 is injected into the waveguides from aposition that requires light to be redirected for in-coupling.

The illustrated set 660 of stacked waveguides includes waveguides 670,680, and 690. Each waveguide includes an associated in-coupling opticalelement (which may also be referred to as a light input area on thewaveguide), with, e.g., in-coupling optical element 700 disposed on amajor surface (e.g., an upper major surface) of waveguide 670,in-coupling optical element 710 disposed on a major surface (e.g., anupper major surface) of waveguide 680, and in-coupling optical element720 disposed on a major surface (e.g., an upper major surface) ofwaveguide 690. In some embodiments, one or more of the in-couplingoptical elements 700, 710, 720 may be disposed on the bottom majorsurface of the respective waveguide 670, 680, 690 (particularly wherethe one or more in-coupling optical elements are reflective, deflectingoptical elements). As illustrated, the in-coupling optical elements 700,710, 720 may be disposed on the upper major surface of their respectivewaveguide 670, 680, 690 (or the top of the next lower waveguide),particularly where those in-coupling optical elements are transmissive,deflecting optical elements. In some embodiments, the in-couplingoptical elements 700, 710, 720 may be disposed in the body of therespective waveguide 670, 680, 690. In some embodiments, as discussedherein, the in-coupling optical elements 700, 710, 720 are wavelengthselective, such that they selectively redirect one or more wavelengthsof light, while transmitting other wavelengths of light. Whileillustrated on one side or corner of their respective waveguide 670,680, 690, it will be appreciated that the in-coupling optical elements700, 710, 720 may be disposed in other areas of their respectivewaveguide 670, 680, 690 in some embodiments.

As illustrated, the in-coupling optical elements 700, 710, 720 may belaterally offset from one another, as seen in the illustrated head-onview in a direction of light propagating to these in-coupling opticalelements. In some embodiments, each in-coupling optical element may beoffset such that it receives light without that light passing throughanother in-coupling optical element. For example, each in-couplingoptical element 700, 710, 720 may be configured to receive light from adifferent image injection device 360, 370, 380, 390, and 400 as shown inFIG. 6 , and may be separated (e.g., laterally spaced apart) from otherin-coupling optical elements 700, 710, 720 such that it substantiallydoes not receive light from the other ones of the in-coupling opticalelements 700, 710, 720.

Each waveguide also includes associated light distributing elements,with, e.g., light distributing elements 730 disposed on a major surface(e.g., a top major surface) of waveguide 670, light distributingelements 740 disposed on a major surface (e.g., a top major surface) ofwaveguide 680, and light distributing elements 750 disposed on a majorsurface (e.g., a top major surface) of waveguide 690. In some otherembodiments, the light distributing elements 730, 740, 750, may bedisposed on a bottom major surface of associated waveguides 670, 680,690, respectively. In some other embodiments, the light distributingelements 730, 740, 750, may be disposed on both top and bottom majorsurface of associated waveguides 670, 680, 690, respectively; or thelight distributing elements 730, 740, 750, may be disposed on differentones of the top and bottom major surfaces in different associatedwaveguides 670, 680, 690, respectively.

The waveguides 670, 680, 690 may be spaced apart and separated by, e.g.,gas, liquid, and/or solid layers of material. For example, asillustrated, layer 760 a may separate waveguides 670 and 680; and layer760 b may separate waveguides 680 and 690. In some embodiments, thelayers 760 a and 760 b are formed of low refractive index materials(that is, materials having a lower refractive index than the materialforming the immediately adjacent one of waveguides 670, 680, 690).Preferably, the refractive index of the material forming the layers 760a, 760 b is 0.05 or more, or 0.10 or less than the refractive index ofthe material forming the waveguides 670, 680, 690. Advantageously, thelower refractive index layers 760 a, 760 b may function as claddinglayers that facilitate total internal reflection (TIR) of light throughthe waveguides 670, 680, 690 (e.g., TIR between the top and bottom majorsurfaces of each waveguide). In some embodiments, the layers 760 a, 760b are formed of air. While not illustrated, it will be appreciated thatthe top and bottom of the illustrated set 660 of waveguides may includeimmediately neighboring cladding layers.

Preferably, for ease of manufacturing and other considerations, thematerial forming the waveguides 670, 680, 690 are similar or the same,and the material forming the layers 760 a, 760 b are similar or thesame. In some embodiments, the material forming the waveguides 670, 680,690 may be different between one or more waveguides, and/or the materialforming the layers 760 a, 760 b may be different, while still holding tothe various refractive index relationships noted above.

With continued reference to FIG. 9A, light rays 770, 780, 790 areincident on the set 660 of waveguides. It will be appreciated that thelight rays 770, 780, 790 may be injected into the waveguides 670, 680,690 by one or more image injection devices 360, 370, 380, 390, 400 (FIG.6 ).

In some embodiments, the light rays 770, 780, 790 have differentproperties, e.g., different wavelengths or different ranges ofwavelengths, which may correspond to different colors. The in-couplingoptical elements 700, 710, 720 each deflect the incident light such thatthe light propagates through a respective one of the waveguides 670,680, 690 by TIR. In some embodiments, the in-coupling optical elements700, 710, 720 each selectively deflect one or more particularwavelengths of light, while transmitting other wavelengths to anunderlying waveguide and associated in-coupling optical element.

For example, in-coupling optical element 700 may be configured todeflect ray 770, which has a first wavelength or range of wavelengths,while transmitting rays 780 and 790, which have different second andthird wavelengths or ranges of wavelengths, respectively. Thetransmitted ray 780 impinges on and is deflected by the in-couplingoptical element 710, which is configured to deflect light of a secondwavelength or range of wavelengths. The ray 790 is deflected by thein-coupling optical element 720, which is configured to selectivelydeflect light of third wavelength or range of wavelengths.

With continued reference to FIG. 9A, the deflected light rays 770, 780,790 are deflected so that they propagate through a correspondingwaveguide 670, 680, 690; that is, the in-coupling optical elements 700,710, 720 of each waveguide deflects light into that correspondingwaveguide 670, 680, 690 to in-couple light into that correspondingwaveguide. The light rays 770, 780, 790 are deflected at angles thatcause the light to propagate through the respective waveguide 670, 680,690 by TIR. The light rays 770, 780, 790 propagate through therespective waveguide 670, 680, 690 by TIR until impinging on thewaveguide's corresponding light distributing elements 730, 740, 750.

With reference now to FIG. 9B, a perspective view of an example of theplurality of stacked waveguides of FIG. 9A is illustrated. As notedabove, the in-coupled light rays 770, 780, 790, are deflected by thein-coupling optical elements 700, 710, 720, respectively, and thenpropagate by TIR within the waveguides 670, 680, 690, respectively. Thelight rays 770, 780, 790 then impinge on the light distributing elements730, 740, 750, respectively. The light distributing elements 730, 740,750 deflect the light rays 770, 780, 790 so that they propagate towardsthe out-coupling optical elements 800, 810, 820, respectively.

In some embodiments, the light distributing elements 730, 740, 750 areorthogonal pupil expanders (OPE's). In some embodiments, the OPE'sdeflect or distribute light to the out-coupling optical elements 800,810, 820 and, in some embodiments, may also increase the beam or spotsize of this light as it propagates to the out-coupling opticalelements. In some embodiments, the light distributing elements 730, 740,750 may be omitted and the in-coupling optical elements 700, 710, 720may be configured to deflect light directly to the out-coupling opticalelements 800, 810, 820. For example, with reference to FIG. 9A, thelight distributing elements 730, 740, 750 may be replaced without-coupling optical elements 800, 810, 820, respectively. In someembodiments, the out-coupling optical elements 800, 810, 820 are exitpupils (EP's) or exit pupil expanders (EPE's) that direct light in aviewer's eye 210 (FIG. 7 ). It will be appreciated that the OPE's may beconfigured to increase the dimensions of the eye box in at least oneaxis and the EPE's may be to increase the eye box in an axis crossing,e.g., orthogonal to, the axis of the OPEs. For example, each OPE may beconfigured to redirect a portion of the light striking the OPE to an EPEof the same waveguide, while allowing the remaining portion of the lightto continue to propagate down the waveguide. Upon impinging on the OPEagain, another portion of the remaining light is redirected to the EPE,and the remaining portion of that portion continues to propagate furtherdown the waveguide, and so on. Similarly, upon striking the EPE, aportion of the impinging light is directed out of the waveguide towardsthe user, and a remaining portion of that light continues to propagatethrough the waveguide until it strikes the EP again, at which timeanother portion of the impinging light is directed out of the waveguide,and so on. Consequently, a single beam of in-coupled light may be“replicated” each time a portion of that light is redirected by an OPEor EPE, thereby forming a field of cloned beams of light, as shown inFIG. 6 . In some embodiments, the OPE and/or EPE may be configured tomodify a size of the beams of light.

Accordingly, with reference to FIGS. 9A and 9B, in some embodiments, theset 660 of waveguides includes waveguides 670, 680, 690; in-couplingoptical elements 700, 710, 720; light distributing elements (e.g.,OPE's) 730, 740, 750; and out-coupling optical elements (e.g., EP's)800, 810, 820 for each component color. The waveguides 670, 680, 690 maybe stacked with an air gap/cladding layer between each one. Thein-coupling optical elements 700, 710, 720 redirect or deflect incidentlight (with different in-coupling optical elements receiving light ofdifferent wavelengths) into its waveguide. The light then propagates atan angle which will result in TIR within the respective waveguide 670,680, 690. In the example shown, light ray 770 (e.g., blue light) isdeflected by the first in-coupling optical element 700, and thencontinues to bounce down the waveguide, interacting with the lightdistributing element (e.g., OPE's) 730 and then the out-coupling opticalelement (e.g., EPs) 800, in a manner described earlier. The light rays780 and 790 (e.g., green and red light, respectively) will pass throughthe waveguide 670, with light ray 780 impinging on and being deflectedby in-coupling optical element 710. The light ray 780 then bounces downthe waveguide 680 via TIR, proceeding on to its light distributingelement (e.g., OPEs) 740 and then the out-coupling optical element(e.g., EP's) 810. Finally, light ray 790 (e.g., red light) passesthrough the waveguide 690 to impinge on the light in-coupling opticalelements 720 of the waveguide 690. The light in-coupling opticalelements 720 deflect the light ray 790 such that the light raypropagates to light distributing element (e.g., OPEs) 750 by TIR, andthen to the out-coupling optical element (e.g., EPs) 820 by TIR. Theout-coupling optical element 820 then finally out-couples the light ray790 to the viewer, who also receives the out-coupled light from theother waveguides 670, 680.

FIG. 9C illustrates a top-down plan view of an example of the pluralityof stacked waveguides of FIGS. 9A and 9B. It will be appreciated thatthis top-down view may also be referred to as a head-on view, as seen inthe direction of propagation of light towards the in-coupling opticalelements 800, 810, 820; that is, the top-down view is a view of thewaveguides with image light incident normal to the page. As illustrated,the waveguides 670, 680, 690, along with each waveguide's associatedlight distributing element 730, 740, 750 and associated out-couplingoptical element 800, 810, 820, may be vertically aligned. However, asdiscussed herein, the in-coupling optical elements 700, 710, 720 are notvertically aligned; rather, the in-coupling optical elements arepreferably non-overlapping (e.g., laterally spaced apart as seen in thetop-down view). As discussed further herein, this nonoverlapping spatialarrangement facilitates the injection of light from different sourcesinto different waveguides on a one-to-one basis, thereby allowing aspecific light source to be uniquely coupled to a specific waveguide. Insome embodiments, arrangements including nonoverlappingspatially-separated in-coupling optical elements may be referred to as ashifted pupil system, and the in-coupling optical elements within thesearrangements may correspond to sub-pupils.

It will be appreciated that the spatially overlapping areas may havelateral overlap of 70% or more, 80% or more, or 90% or more of theirareas, as seen in the top-down view. On the other hand, the laterallyshifted areas of less than 30% overlap, less than 20% overlap, or lessthan 10% overlap of their areas, as seen in top-down view. In someembodiments, laterally shifted areas have no overlap.

FIG. 9D illustrates a top-down plan view of another example of aplurality of stacked waveguides. As illustrated, the waveguides 670,680, 690 may be vertically aligned. However, in comparison to theconfiguration of FIG. 9C, separate light distributing elements 730, 740,750 and associated out-coupling optical elements 800, 810, 820 areomitted. Instead, light distributing elements and out-coupling opticalelements are effectively superimposed and occupy the same area as seenin the top-down view. In some embodiments, light distributing elements(e.g., OPE's) may be disposed on one major surface of the waveguides670, 680, 690 and out-coupling optical elements (e.g., EPE's) may bedisposed on the other major surface of those waveguides. Thus, eachwaveguide 670, 680, 690 may have superimposed light distributing and outcoupling optical elements, collectively referred to as combinedOPE/EPE's 1281, 1282, 1283, respectively. Further details regarding suchcombined OPE/EPE's may be found in U.S. application Ser. No. 16/221,359,filed on Dec. 14, 2018, the entire disclosure of which is incorporatedby reference herein. The in-coupling optical elements 700, 710, 720in-couple and direct light to the combined OPE/EPE's 1281, 1282, 1283,respectively. In some embodiments, as illustrated, the in-couplingoptical elements 700, 710, 720 may be laterally shifted (e.g., they arelaterally spaced apart as seen in the illustrated top-down view) in havea shifted pupil spatial arrangement. As with the configuration of FIG.9C, this laterally-shifted spatial arrangement facilitates the injectionof light of different wavelengths (e.g., from different light sources)into different waveguides on a one-to-one basis.

FIG. 9E illustrates an example of wearable display system 60 into whichthe various waveguides and related systems disclosed herein may beintegrated. In some embodiments, the display system 60 is the system 250of FIG. 6 , with FIG. 6 schematically showing some parts of that system60 in greater detail. For example, the waveguide assembly 260 of FIG. 6may be part of the display 70.

With continued reference to FIG. 9E, the display system 60 includes adisplay 70, and various mechanical and electronic modules and systems tosupport the functioning of that display 70. The display 70 may becoupled to a frame 80, which is wearable by a display system user orviewer 90 and which is configured to position the display 70 in front ofthe eyes of the user 90. The display 70 may be considered eyewear insome embodiments. The display 70 may include one or more waveguides,such as the waveguide 270, configured to relay in-coupled image lightand to output that image light to an eye of the user 90. In someembodiments, a speaker 100 is coupled to the frame 80 and configured tobe positioned adjacent the ear canal of the user 90 (in someembodiments, another speaker, not shown, may optionally be positionedadjacent the other ear canal of the user to provide stereo/shapeablesound control). The display system 60 may also include one or moremicrophones 110 or other devices to detect sound. In some embodiments,the microphone is configured to allow the user to provide inputs orcommands to the system 60 (e.g., the selection of voice menu commands,natural language questions, etc.), and/or may allow audio communicationwith other persons (e.g., with other users of similar display systems.The microphone may further be configured as a peripheral sensor tocollect audio data (e.g., sounds from the user and/or environment). Insome embodiments, the display system 60 may further include one or moreoutwardly-directed environmental sensors 112 configured to detectobjects, stimuli, people, animals, locations, or other aspects of theworld around the user. For example, environmental sensors 112 mayinclude one or more cameras, which may be located, for example, facingoutward so as to capture images similar to at least a portion of anordinary field of view of the user 90. In some embodiments, the displaysystem may also include a peripheral sensor 120 a, which may be separatefrom the frame 80 and attached to the body of the user 90 (e.g., on thehead, torso, an extremity, etc. of the user 90). The peripheral sensor120 a may be configured to acquire data characterizing a physiologicalstate of the user 90 in some embodiments. For example, the sensor 120 amay be an electrode.

With continued reference to FIG. 9E, the display 70 is operativelycoupled by communications link 130, such as by a wired lead or wirelessconnectivity, to a local data processing module 140 which may be mountedin a variety of configurations, such as fixedly attached to the frame80, fixedly attached to a helmet or hat worn by the user, embedded inheadphones, or otherwise removably attached to the user 90 (e.g., in abackpack-style configuration, in a belt-coupling style configuration).Similarly, the sensor 120 a may be operatively coupled by communicationslink 120 b, e.g., a wired lead or wireless connectivity, to the localprocessor and data module 140. The local processing and data module 140may comprise a hardware processor, as well as digital memory, such asnon-volatile memory (e.g., flash memory or hard disk drives), both ofwhich may be utilized to assist in the processing, caching, and storageof data. Optionally, the local processor and data module 140 may includeone or more central processing units (CPUs), graphics processing units(GPUs), dedicated processing hardware, and so on. The data may includedata a) captured from sensors (which may be, e.g., operatively coupledto the frame 80 or otherwise attached to the user 90), such as imagecapture devices (such as cameras), microphones, inertial measurementunits, accelerometers, compasses, GPS units, radio devices, gyros,and/or other sensors disclosed herein; and/or b) acquired and/orprocessed using remote processing module 150 and/or remote datarepository 160 (including data relating to virtual content), possiblyfor passage to the display 70 after such processing or retrieval. Thelocal processing and data module 140 may be operatively coupled bycommunication links 170, 180, such as via a wired or wirelesscommunication links, to the remote processing module 150 and remote datarepository 160 such that these remote modules 150, 160 are operativelycoupled to each other and available as resources to the local processingand data module 140. In some embodiments, the local processing and datamodule 140 may include one or more of the image capture devices,microphones, inertial measurement units, accelerometers, compasses, GPSunits, radio devices, and/or gyros. In some other embodiments, one ormore of these sensors may be attached to the frame 80, or may bestandalone structures that communicate with the local processing anddata module 140 by wired or wireless communication pathways.

With continued reference to FIG. 9E, in some embodiments, the remoteprocessing module 150 may comprise one or more processors configured toanalyze and process data and/or image information, for instanceincluding one or more central processing units (CPUs), graphicsprocessing units (GPUs), dedicated processing hardware, and so on. Insome embodiments, the remote data repository 160 may comprise a digitaldata storage facility, which may be available through the internet orother networking configuration in a “cloud” resource configuration. Insome embodiments, the remote data repository 160 may include one or moreremote servers, which provide information, e.g., information forgenerating virtual content, to the local processing and data module 140and/or the remote processing module 150. In some embodiments, all datais stored and all computations are performed in the local processing anddata module, allowing fully autonomous use from a remote module.Optionally, an outside system (e.g., a system of one or more processors,one or more computers) that includes CPUs, GPUs, and so on, may performat least a portion of processing (e.g., generating image information,processing data) and provide information to, and receive informationfrom, modules 140, 150, 160, for instance via wireless or wiredconnections.

FIG. 10 illustrates an example of a wearable display system with a lightprojection system 910 having a spatial light modulator 930 and aseparate light source 940. The light source 940 may comprise one or morelight emitters and illuminates the spatial light modulator (SLM) 930. Alens structure 960 may be used to focus the light from the light source940 onto the SLM 930. A beam splitter (e.g., a polarizing beam splitter(PBS)) 950 reflects light from the light source 940 to the spatial lightmodulator 930, which reflects and modulates the light. The reflectedmodulated light, also referred to as image light, then propagatesthrough the beam splitter 950 to the eyepiece 920. Another lensstructure, projection optics 970, may be utilized to converge or focusthe image light onto the eyepiece 920. The eyepiece 920 may include oneor more waveguides or waveguides that relay the modulated to the eye210.

As noted herein, the separate light source 940 and associated lensstructure 960 may undesirably add weight and size to the wearabledisplay system. This may decrease the comfort of the display system,particularly for a user wearing the display system for an extendedduration.

In addition, the light source 940 in conjunction with the SLM 930 mayconsume energy inefficiently. For example, the light source 940 mayilluminate the entirety of the SLM 930. The SLM 930 then selectivelyreflects light towards the eyepiece 920. thus, not all the lightproduced by the light source 940 may be utilized to form an image; someof this light, e.g., light corresponding to dark regions of an image, isnot reflected to the eyepiece 920. As a result, the light source 940utilizes energy to generate light to illuminate the entirety of the SLM930, but only a fraction of this light may be needed to form someimages.

Moreover, as noted herein, in some cases, the SLM 930 may modulate lightusing a micro-mirror to selectively reflect incident light, or usingliquid crystal molecules that modify the amount of light reflected froman underlying mirror. As a result, such devices require physicalmovement of optical elements (e.g., micro-mirrors or liquid crystalmolecules such as in LCoS or DLP panels, respectively) in order tomodulate light from the light source 940. The physical movement requiredto modulate light to encode the light with image information, e.g.,corresponding to a pixel, may occur at relatively slow speeds incomparison to, e.g., the ability to turn an LED or OLED “on” or “off”.This relatively slow movement may limit the frame rate of the displaysystem and may be visible as, e.g., motion blur, color-breakup, and/orpresented images that are mismatched with the pose of the user's head orchanges in said pose.

Advantageously, wearable displays utilizing emissive micro-displays, asdisclosed herein, may facilitate wearable display systems that have arelatively low weight and bulkiness, high energy efficiency, and highframe rate, with low motion blur and low motion-to-photon latency. Lowblur and low motion-to-photon latency are further discussed in U.S.Provisional Application No. 62/786,199, filed Dec. 28, 2018, the entiredisclosure of which is incorporated by reference herein. In addition, incomparison to scanning fiber displays, the emissive micro-displays mayavoid artifacts caused by the use of coherent light sources.

With reference now to FIG. 11A, an example is illustrated of a wearabledisplay system with a light projection system 1010 having multipleemissive micro-displays 1030 a, 1030 b, 1030 c. Light from themicro-displays 1030 a, 1030 b, 1030 c is combined by an optical combiner1050 and directed towards an eyepiece 1020, which relays the light tothe eye 210 of a user. Projection optics 1070 may be provided betweenthe optical combiner 1050 and the eyepiece 1020. In some embodiments,the eyepiece 1020 may be a waveguide assembly comprising one or morewaveguides. In some embodiments, the light projection system 1010 andthe eyepiece 1020 may be supported (e.g., attached to) the frame 80(FIG. 9E).

In some embodiments, the micro-displays 1030 a, 1030 b, 1030 c may bemonochrome micro-displays, with each monochrome micro-display outputtinglight of a different component color to provide a monochrome image. Asdiscussed herein, the monochrome images combine to form a full-colorimage.

In some other embodiments, the micro-displays 1030 a, 1030 b, 1030 c maybe may each be full-color displays configured to output light of allcomponent colors. For example, the micro-displays 1030 a, 1030 b, 1030 ceach include red, green, and blue light emitters. The micro-displays1030 a, 1030 b, 1030 c may be identical and may display the same image.However, utilizing multiple micro-displays may provide advantages forincreasing the brightness and brightness dynamic range of the brightnessof the image, by combining the light from the multiple micro-displays toform a single image. In some embodiments, two or more (e.g., three)micro-displays may be utilized, with the optical combiner 1050 isconfigured to combine light from all of these micro-displays.

The micro-displays may comprise an array of light emitters. Examples oflight emitters include organic light-emitting diodes (OLEDs) andmicro-light-emitting diodes (micro-LEDs). It will be appreciated thatOLEDs utilize organic material to emit light and micro-LEDs utilizeinorganic material to emit light. Advantageously, some micro-LEDsprovide higher luminance and higher efficiency (in terms of lux/W) thanOLEDs. In some embodiments, the micro-displays are preferably emissivemicro-LED displays.

With continued reference to FIG. 11A, the micro-displays 1030 a, 1030 b,1030 c may each be configured to emit image light 1032 a, 1032 b, 1032c. Where the micro-displays are monochrome micro-displays, the imagelight 1032 a, 1032 b, 1032 c may each be of a different component color.The optical combiner 1050 receives the image light 1032 a, 1032 b, 1032c and effectively combines this light such that the light propagatesgenerally in the same direction, e.g., toward the projection optics1070. In some embodiments, the optical combiner 1050 may be a dichroicX-cube prism having reflective internal surfaces that redirect the imagelight 1032 a, 1032 b, 1032 c to the projection optics 1070. It will beappreciated that the projection optics 1070 may be a lens structurecomprising one or more lenses which converge or focus image light ontothe eyepiece 1020. The eyepiece 1020 then relays the image light 1032 a,1032 b, 1032 c to the eye 210.

In some embodiments, the eyepiece 1020 may comprise a plurality ofstacked waveguides 1020 a, 1020 b, 1020 c, each of which has arespective in-coupling optical element 1022 a, 1022 b, 1022 c. In someembodiments, the number of waveguides is proportional to the number ofcomponent colors provided by the micro-displays 1030 a, 1030 b, 1030 c.For example, where there are three component colors, the number ofwaveguides in the eyepiece 1020 may include a set of three waveguides ormultiple sets of three waveguides each. In some embodiments, each setmay output light with wavefront divergence corresponding to a particulardepth plane, as discussed herein. It will be appreciated that thewaveguides 1020 a, 1020 b, 1020 c and the in-coupling optical element1022 a, 1022 b, 1022 c may correspond to the waveguides 670, 680, 690and the in-coupling optical elements 700, 710, 720, respectively, ofFIGS. 9A-9C. As viewed from the projection optics 1070, the in-couplingoptical elements 1022 a, 1022 b, 1022 c may be laterally shifted, suchthat they at least partly do not overlap as seen in such a view.

As illustrated, the various in-coupling optical elements disclosedherein (e.g., the in-coupling optical element 1022 a, 1022 b, 1022 c)may be disposed on a major surface of an associated waveguide (e.g.,waveguides 1020 a, 1020 b, 1020 c, respectively). In addition, as alsoillustrated, the major surface on which a given in-coupling opticalelement is disposed may be the rear surface of the waveguide. In such aconfiguration, the in-coupling optical element may be a reflective lightredirecting element, which in-couples light by reflecting the light atangles which support TIR through the associated waveguide. In some otherconfigurations, the in-coupling optical element may be disposed on theforward surface of the waveguide (closer to the projection optics 1070than the rearward surface). In such configurations, the in-couplingoptical element may be a transmissive light redirecting element, whichin-couples light by changing the direction of propagation of light asthe light is transmitted through the in-coupling optical element. Itwill be appreciated that any of the in-coupling optical elementsdisclosed herein may be reflective or transmissive in-coupling opticalelements.

With continued reference to FIG. 11A, image light 1032 a, 1032 b, 1032 cfrom different ones of the micro-displays 1030 a, 1030 b, 1030 c maytake different paths to the eyepiece 1020, such that they impinge ondifferent ones of the in-coupling optical element 1022 a, 1022 b, 1022c. Where the image light 1032 a, 1032 b, 1032 c includes light ofdifferent component colors, the associated in-coupling optical element1022 a, 1022 b, 1022 c, respectively, may be configured to selectivelyin couple light of different wavelengths, as discussed above regarding,e.g., the in-coupling optical elements 700, 710, 720 of FIGS. 9A-9C.

With continued reference to FIG. 11A, the optical combiner 1050 may beconfigured to redirect the image light 1032 a, 1032 b, 1032 c emitted bythe micro-displays 1030 a, 1030 b, 1030 c such that the image lightpropagates along different optical paths, in order to impinge on theappropriate associated one of the in-coupling optical element 1022 a,1022 b, 1022 c. Thus, the optical combiner 1050 combines the image light1032 a, 1032 b, 1032 c in the sense that the image light is outputtedfrom a common face of the optical combiner 1050, although light may exitthe optical combiner in slightly different directions. For example, thereflective internal surfaces 1052, 1054 of the X-cube prism may each beangled to direct the image light 1032 a, 1032 b, 1032 c along differentpaths to the eyepiece 1020. As a result, the image light 1032 a, 1032 b,1032 c may be incident on different associated ones of in-couplingoptical elements 1022 a, 1022 b, 1022 c. In some embodiments, themicro-displays 1030 a, 1030 b, 1030 c may be appropriately angledrelative to the reflective internal surfaces 1052, 1054 of the X-cubeprism to provide the desired light paths to the in-coupling opticalelements 1022 a, 1022 b, 1022 c. For example, faces of one or more ofthe micro-displays 1030 a, 1030 b, 1030 c may be angled to matchingfaces of the optical combiner 1050, such that image light emitted by themicro-displays is incident on the reflective internal surfaces 1052,1054 at an appropriate angle to propagate towards the associated incoupling optical element 1022 a, 1022 b, or 1022 c. It will beappreciated that, in addition to a cube, the optical combiner 1050 maytake the form of various other polyhedra. For example, the opticalcombiner 1050 may be in the shape of a rectangular prism having at leasttwo faces that are not squares.

With continued reference to FIG. 11A, in some embodiments, themonochrome micro-display 1030 b directly opposite the output face 1051may advantageously output green light. It will be appreciated that thereflective surfaces 1052, 1054 may have optical losses when reflectinglight from the micro-displays. In addition, the human eye is mostsensitive to the color green. Consequently, the monochrome micro-display1030 b opposite the output face 1051 preferably outputs green light, sothat the green light may proceed directly through the optical combiner1050 without needing to be reflected to be outputted from the opticalcombiner 1050. It will be appreciated, however, that the greenmonochrome micro-display may face other surfaces of the optical combiner1050 in some other embodiments.

As discussed herein, the perception of a full color image by a user maybe achieved with time division multiplexing in some embodiments. Forexample, different ones of the emissive micro-displays 1030 a, 1030 b,1030 c may be activated at different times to generate differentcomponent color images. In such embodiments, the different componentcolor images that form a single full color image may be sequentiallydisplayed sufficiently quickly that the human visual system does notperceive the component color images as being displayed at differenttimes; that is, the different component color images that form a singlefull color image may all be displayed within a duration that issufficiently short that the user perceives the component color images asbeing simultaneously presented, rather than being temporally separated.For example, it will be appreciated that the human visual system mayhave a flicker fusion threshold. The flicker fusion threshold may beunderstood to a duration within which the human visual system is unableto differentiate images as being presented at different times. Imagespresented within that duration are fused or combined and, as a result,may be perceived by a user to be present simultaneously. Flickeringimages with temporal gaps between the images that are outside of thatduration are not combined, and the flickering of the images isperceptible. In some embodiments, the duration is 1/60 seconds or less,which corresponds to a frame rate of 60 Hz or more. Preferably, imageframes for any individual eye are provided to the user at a frame rateequal to or higher than the duration of the flicker fusion threshold ofthe user. For example, the frame rate for each of the left-eye orright-eye pieces may be 60 Hz or more, or 120 Hz or more; and, as aresult, the frame rate provided by the light projection system 1010 maybe 120 Hz or more, or 240 Hz or more in some embodiments.

It will be appreciated that time division multiplexing mayadvantageously reduce the computational load on processors (e.g.,graphics processors) utilized to form displayed images. In some otherembodiments, such as where sufficient computational resources areavailable, all component color images that form a full color image maybe displayed simultaneously by the micro-displays 1030 a, 1030 b, 1030c.

As discussed herein, the micro-displays 1030 a, 1030 b, 1030 c may eachinclude arrays of light emitters. FIG. 11B illustrates an example of anarray 1042 of light emitters 1044. Where the associated micro-display isa monochrome micro-display, the light emitters 1044 may all beconfigured to emit light of the same color.

Where the associated micro-display is a full-color micro-display,different ones of the light emitters 1044 may be configured to emitlight of different colors. In such embodiments, the light emitters 1044may be considered subpixels and may be arranged in groups, with eachgroup having at least one light emitter configured to emit light of eachcomponent color. For example, where the component colors are red, green,and blue, each group may have at least one red subpixel, at least onegreen subpixel, in at least one blue subpixel.

It will be appreciated, that while the light emitters 1044 are shownarranged in a grid pattern for ease of illustration, the light emitters1044 may have other regularly repeating spatial arrangements. Forexample, the number of light emitters of different component colors mayvary, the sizes of the light emitters may vary, the shapes of the lightemitters and/or the shapes made out by groups of light emitters mayvary, etc.

With continued reference to FIG. 11B, it will be appreciated that themicro-emitters 1044 emit light. In addition, manufacturing constraints,such as lithography or other patterning and processing limitations,and/or electrical considerations, may limit how closely neighboringlight-emitters 1044 are spaced. As a result, there may be an area 1045surrounding the light emitter 1044 within which it is not practical toform other light emitters 1044. This area 1045 forms the inter-emitterregions between light emitters 1044. In some embodiments, taking intoaccount the area 1045, the light emitters have a pitch of, e.g., lessthan 10 μm, less than 8 μm, less than 6 μm, or less than 5 μm, and morethan 1 μm, including 1-5 μm, and an emitter size of 2 μm or less, 1.7 μmor less, or 1.3 μm or less. In some embodiments, the emitter size iswithin a range having an upper limit of the above-noted sizes and alower limit of 1 μm. In some embodiments, the ratio of emitter size topitch is 1:1 to 1:5, 1:2 to 1:4, or 1:2 to 1:3.

It will be appreciated that, given some light emitter devicearchitectures and materials, current crowding may decrease the emitter'sefficiency and pixel droop may cause unintentional activation of pixels(e.g., due to energy directed to one light emitter bleeding into aneighboring light emitter). As a result, a relatively large area 1045may beneficially reduce current crowding and pixel droop. In someembodiments, the ratio of emitter size to pitch is preferably 1:2 to1:4, or 1:2 to 1:3.

It will also be appreciated, however, that large separations betweenlight emitters (e.g., a small light emitter to pitch ratio) mayundesirably cause visible gaps, or dark regions, between the lightemitters. Even when laterally translated as discussed herein, some gapsmay still be visible, depending on the size of the original gap, thedistance of the translation, and the number of subframes (and resultingtranslation increments) utilized. In some embodiments, lens structuresuch as light collimators may be utilized to effectively fill orpartially fill in these dark regions. For example, a light collimatinglens may extend on and around a light emitter 1044, such that light fromthe emitter 1044 completely fills the lens. For example, the lightcollimating lens may have a larger width than the light emitters 1044and, in some embodiments, the width of the collimating lens may beapproximately equal to the pitch. As a result, the size of the emitter1044 is effectively increased to extend across the area of the lens,thereby filling in some or all of the area 1045. In some otherembodiments, the width of the collimating lens may be approximatelyequal to the distance that the projection system is translated, asdiscussed herein, for each subframe. Lens structures such as lightcollimators are further discussed herein (e.g., in FIG. 30A and therelated discussion).

As discussed herein, the light emitters 1044 may be OLEDs or micro-LEDs.It will be appreciated that OLEDs may utilize layers of organicmaterial, e.g., disposed between electrodes, to emit light. Micro-LEDsmay utilize inorganic materials, e.g., Group III-V materials such asGaAs, GaN, and/or GaIn for light emission. Examples of GaN materialsinclude InGaN, which may be used to form blue or green light emitters insome embodiments. Examples of GaIn materials include AlGaInP, which maybe used to form red light emitters in some embodiments. In someembodiments, the light emitters 1044 may emit light of an initial color,which may be converted to other desired colors using phosphor materialsor quantum dots. For example, the light emitter may emit blue lightwhich excites a phosphor material or quantum dot that converts the bluewavelength light to green or red wavelengths.

With reference now to FIG. 12 , another example is illustrated of awearable display system with a light projection system having multipleemissive micro-displays 1030 a, 1030 b, 1030 c. The illustrated displaysystem is similar to the display system of FIG. 11A except that theoptical combiner 1050 has a standard X-cube prism configuration andincludes light redirecting structures 1080 a and 1080 c for modifyingthe angle of incidence of light on the reflective surfaces 1052, 1054 ofthe X-cube prism. It will be appreciated that a standard X-cube prismconfiguration will receive light which is normal to a face of the X-cubeand redirect this light 45° such that it is output at a normal anglefrom a transverse face of the X-cube. However, this would cause theimage light 1032 a, 1032 b, 1032 c to be incident on the samein-coupling optical element of the eyepiece 1020. In order to providedifferent paths for the image light 1032 a, 1032 b, 1032 c, so that theimage light is incident on associated ones of the in-coupling opticalelements 1022 a, 1022 b, 1022 c of the waveguide assembly, the lightredirecting structures 1080 a, 1080 c may be utilized.

In some embodiments, the light redirecting structures 1080 a, 1080 c maybe lens structures. It will be appreciated that the lens structures maybe configured to receive incident light and to redirect the incidentlight at an angle such that the light reflects off a corresponding oneof the reflective surfaces 1052, 1054 and propagates along a light pathtowards a corresponding one of the in-coupling optical elements 1022 a,1022 c. As examples, the light redirecting structures 1080 a, 1080 c maycomprise micro-lenses, nano-lenses, reflective wells, metasurfaces, andliquid crystal gratings. In some embodiments, the micro-lenses,nano-lenses, reflective wells, metasurfaces, and liquid crystal gratingsmay be organized in arrays. For example, each light emitter of themicro-displays 1030 a, 1030 c may be matched with one micro-lens. Insome embodiments, in order to redirect light in a particular direction,the micro-lens or reflective wells may be asymmetrical and/or the lightemitters may be disposed off-center relative to the micro-lens. Inaddition, in some embodiments, the light redirecting structures 1080 a,1080 c may be collimators which narrow the angular emission profiles ofassociated light emitters, to increase the amount of light ultimatelyin-coupled into the eyepiece 1020. Further details regarding such lightredirecting structures 1080 a, 1080 c are discussed below regardingFIGS. 24A-27C.

With reference now to FIG. 13A, in some embodiments, two or more of thein-coupling optical elements 1022 a, 1022 b, 1022 c may overlap (e.g.,as seen in a head-on view in the direction of light propagation into thein-coupling optical element 1022 a, 1022 b, 1022 c). FIG. 13Aillustrates an example of a side-view of a wearable display system witha light projection system 1010 having multiple emissive micro-displays1032 a, 1032 b, 1032 c and an eyepiece 1020 with overlapping lightin-coupling optical elements 1022 a, 1022 c and non-overlapping lightin-coupling optical element 1022 b. As illustrated, the in-couplingoptical elements 1022 a, 1022 c overlap, while the in-coupling opticalelements 1022 b are laterally shifted. Stated another way, thein-coupling optical elements 1022 a, 1022 c are aligned directly in thepaths of the image light 1032 a, 1032 c, while the image light 1032 bfollows another path to the eyepiece 1020, such that it is incident onan area of the eyepiece 1020 that is laterally shifted relative to thearea in which the image light 1032 a, 1032 c is incident.

As illustrated, differences between the paths for the image light 1032 band image light 1032 a, 1032 c may be established using lightredirecting structures 1080 a, 1080 c. In some embodiments, the imagelight 1032 b from the emissive micro-display 1030 b proceeds directlythrough the optical combiner 1052. The image light 1032 a from theemissive micro-display 1032 a is redirected by the light redirectingstructure 1080 a such that it reflects off of the reflective surface1054 and propagates out of the optical combiner 1050 in the samedirection as the image light 1032 c. It will be appreciated that theimage light 1032 c from the emissive micro-display 1032 c is redirectedby the light redirecting structure 1080 c such that it reflects off ofthe reflective surface 1052 at an angle such that the image light 1032 cpropagates out of the optical combiner 1050 in the same direction as theimage light 1032 b. Thus, the redirection of light by the lightredirecting structures 1080 a, 1080 c and the angles of the reflectivesurfaces 1052, 1054 are configured to provide a common path for theimage light 1032 a, 1032 c out of the optical combiner 1050, with thiscommon path being different from the path of the image light 1032 b. Insome other embodiments, one or both of the light redirecting structures1080 a, 1080 c may be omitted and the reflective surfaces 1052, 1054 inthe optical combiner 1050 may be configured to reflect the image light1032 a, 1032 c in the appropriate respective directions such that theyexit the optical combiner 1050 propagating in the same direction, whichis different from the direction of the image light 1032 b. As such,after propagating through the projection optics 1070, the image light1032 a, 1032 c exit from one exit pupil while the image light 1032 bexits from another exit pupil. In this configuration, the lightprojection system 1010 may be referred to as a two-pupil projectionsystem.

In some embodiments, the light projection system 1010 may have a singleoutput pupil and may be referred to as a single-pupil projection system.In such embodiments, the light projection system 1010 may be configuredto direct the image light 1032 a, 1032 b, 1032 c onto a single commonarea of the eyepiece 1020. Such a configuration is shown in FIG. 13B,which illustrates a wearable display system with a light projectionsystem 1010 having multiple emissive micro-displays 1030 a, 1030 b, 1030c configured to direct light to a single light in-coupling area of theeyepiece 1020. In some embodiments, as discussed further herein, theeyepiece 1020 may include a stack of waveguides having overlapping lightin-coupling optical elements. In some other embodiments, a single lightin-coupling optical element may be configured to in-couple light of allcomponent colors into a single waveguide. The display system of FIG. 13Bis similar to the display system of FIG. 13A, except for the omission ofthe light redirecting structures 1080 a, 1080 c and the use of thein-coupling optical element 1122 a and with the associated waveguide1020 a. As illustrated, the in-coupling optical element 1122 ain-couples each of image light 1032 a, 1032 b, 1032 c into the waveguide1020 a, which then relays the image light to the eye 210. In someembodiments, the in-coupling optical element 1122 a may comprise adiffractive grating. In some embodiments, the in-coupling opticalelement 1122 a is a metasurface and/or liquid crystal grating.

As discussed herein, in some embodiments, the emissive micro-displays1030 a, 1030 b, 1030 c may be monochrome micro-displays configured toemit light of different colors. In some embodiments, one or more of theemissive micro-displays 1030 a, 1030 b, 1030 c may have groups of lightemitters configured to emit light of two or more, but not all, componentcolors. For example, a single emissive micro-display may have groups oflight emitters—with at least one light emitter per group configured toemit blue light and at least one light emitter per group configured toemit green light—and a separate emissive micro-display on a differentface of the X-cube 1050 may have light emitters configured to emit redlight. In some other embodiments, the emissive micro-displays 1030 a,1030 b, 1030 c may each be full-color displays, each having lightemitters of all component colors. As noted herein, utilizing multiplesimilar micro-displays may provide advantages for dynamic range andincreased display brightness.

In some embodiments, a single full-color emissive micro-display may beutilized. FIG. 14 illustrates an example of a wearable display systemwith a single emissive micro-display 1030 b. The wearable display systemof FIG. 14 is similar to the wearable display system of FIG. 14 , exceptthat the single emissive micro-display 1030 b is a full colormicro-display configured to emit light of all component colors. Asillustrated, the micro-display 1030 b emits image light 1032 a, 1032 b,1032 c of each component color. In such embodiments, the opticalcombiner 1050 (FIG. 13B) may be omitted, which may advantageously reducethe weight and size of the wearable display system relative to a systemwith an optical combiner.

As discussed above, the in-coupling optical elements of the eyepiece1020 may assume various configurations. Some examples of configurationsfor the eyepiece 1020 are discussed below in relation to FIGS. 15-23C.

FIG. 15 illustrates a side view of an example of an eyepiece 1020 havinga stack of waveguides 1020 a, 1020 b, 1020 c with overlappingin-coupling optical elements 1022 a, 1022 b, 1022 c, respectively. Itwill be appreciated that the illustrated waveguide stack may be utilizedin place of the single illustrated waveguide 1020 a of FIGS. 13B and 14. As discussed herein, each of the in-coupling optical elements 1022 a,1022 b, 1022 c is configured to in-couple light having a specific color(e.g., light of a particular wavelength, or a range of wavelengths). Inthe illustrated orientation of the eyepiece 1020 in which the imagelight propagates vertically down the page towards the eyepiece 1020, thein-coupling optical elements 1022 a, 1022 b, 1022 c are verticallyaligned with each other (e.g., along an axis parallel to the directionof propagation of the image light 1032 a, 1032 b, 1032 c) such that theyspatially overlap with each other as seen in a top down view (a head-onview in a direction of the image light 1032 a, 1032 b, 1032 cpropagating to the in-coupling optical elements).

With continued reference to FIG. 15 , as discussed herein, theprojection system 1010 (FIGS. 13, 14 ) is configured to output a firstmonochrome color image, a second monochrome color image, and a thirdmonochrome color image (e.g., red, green and blue color images) throughthe single-pupil of the projection system, the monochrome images beingformed by the image light 1032 a, 1032 b, 1032 c, respectively. Thein-coupling optical element 1022 c is configured to in-couple the imagelight 1032 c for the first color image into the waveguide 1020 c suchthat it propagates through the waveguide 1020 c by multiple totalinternal reflections at the upper and bottom major surfaces of thewaveguide 1020 c, the in-coupling optical element 1022 b is configuredto in-couple the image light 1032 b for the second color image into thewaveguide 1020 b such that it propagates through the waveguide 1020 b bymultiple total internal reflections at the upper and bottom majorsurfaces of the waveguide 1020 b, and the in-coupling optical element1022 a is configured to in-couple the image light 1032 a for the thirdcolor image into the waveguide 1020 a such that it propagates throughthe waveguide 1020 a by multiple total internal reflections at the upperand bottom major surfaces of the waveguide 1020 a.

As discussed herein, the in-coupling optical element 1022 c ispreferably configured to in-couple substantially all the incident light1032 c corresponding to the first color image into the associatedwaveguide 1020 c while allowing substantially all the incident light1032 b, 1032 a corresponding to the second color image and the thirdcolor image, respectively, to be transmitted without being in-coupled.Similarly, the in-coupling optical element 1022 b is preferablyconfigured to in-couple substantially all the incident image light 1032b corresponding to the second color image into the associated waveguide1020 b while allowing substantially all the incident light correspondingto the third color image to be transmitted without being in-coupled.

It will be appreciated that, in practice, the various in-couplingoptical elements may not have perfect selectivity. For example, some ofthe image light 1032 b, 1032 a may undesirably be in-coupled into thewaveguide 1020 c by the in-coupling optical element 1022 c; and some ofthe incident image light 1032 a may undesirably be in-coupled into thewaveguide 1020 b by the in-coupling optical element 1022 b. Furthermore,some of the image light 1032 c may be transmitted through thein-coupling optical element 1022 c and in-coupled into waveguides 1020 band/or 1020 a by the in-coupling optical elements 1020 b and/or 1020 a,respectively. Similarly, some of the image light 1032 b may betransmitted through the in-coupling optical element 1022 b andin-coupled into waveguide 1020 a by the in-coupling optical element 1022a.

In-coupling image light for a color image into an unintended waveguidemay cause undesirable optical effects, such as, for example cross-talkand/or ghosting. For example, in-coupling of the image light 1032 c forthe first color image into unintended waveguides 1020 b and/or 1020 amay result in undesirable cross-talk between the first color image, thesecond color image and/or the third color image; and/or may result inundesirable ghosting. As another example, in-coupling of the image light1032 b, 1032 a for the second or third color image, respectively, intothe unintended waveguide 1020 c may result in undesirable cross-talkbetween the first color image, the second color image and/or the thirdcolor image; and/or may cause undesirable ghosting. In some embodiments,these undesirable optical effects may be mitigated by providing colorfilters (e.g., absorptive color filters) that may reduce the amount ofincident light that is in-coupled into an unintended waveguide.

FIG. 16 illustrates a side view of an example of a stack of waveguideswith color filters for mitigating ghosting or crosstalk betweenwaveguides. The eyepiece 1020 of FIG. 16 is similar to that of FIG. 15 ,except for the presence of one or more of the color filters 1024 c, 1024b and 1028, 1026. The color filters 1024 c, 1024 b are configured toreduce the amount of light unintentionally in-coupled into thewaveguides 1020 b and 1020 a, respectively. The color filters 1028, 1026are configured to reduce the amount of unintentionally in-coupled imagelight which propagates through the waveguides 1020 b, 1020 c,respectively.

With continued reference to FIG. 16 , a pair of color filters 1026disposed on the upper and lower major surfaces of the waveguide 1020 cmay be configured to absorb image light 1032 a, 1032 b that may havebeen unintentionally been in-coupled into waveguide 1020 c. In someembodiments, the color filter 1024 c disposed between the waveguides1020 c and 1020 b is configured to absorb image light 1032 c that istransmitted through the in-coupling optical element 1022 c without beingin-coupled. A pair of color filters 1028 disposed on the upper and lowermajor surfaces of the waveguide 1020 b is configured to absorb imagelight 1032 a that is in-coupled into waveguide 1020 b. A color filter1024 b disposed between the waveguides 1020 b and 1020 a is configuredto absorb image light 1032 b that is transmitted through the in-couplingoptical element 710.

In some embodiments, the color filters 1026 on each major surface of thewaveguide 1020 c are similar and are configured to absorb light of thewavelengths of both image light 1032 a, 1032 b. In some otherembodiments, the color filter 1026 on one major surface of the waveguide1020 c may be configured to absorb light of the color of image light1032 a, and the color filter on the other major surface may beconfigured to absorb light of the color of image light 1032 b. In eitherarrangement, the color filters 1026 may be configured to selectivelyabsorb the image light 1032 a, 1032 b propagating through the waveguide1020 c by total internal reflection. For example, at TIR bounces of theimage light 1032 a, 1032 b off the major surfaces of the waveguide 1020c, the image light 1032 a, 1032 b contacts a color filter 1026 on thosemajor surfaces and a portion of that image light is absorbed.Preferably, due to the selective absorption of image light 1032 a, 1032b by the colors filters 1026, the propagation of the in-coupled theimage light 1032 c via TIR through the waveguide 1020 c is notappreciably affected.

Similarly, the plurality of color filters 1028 may be configured asabsorption filters that absorb in-coupled image light 1032 a thatpropagates through the waveguide 1020 b by total internal reflection. AtTIR bounces of the image light 1032 a off the major surfaces of thewaveguide 1020 b, the image light 1032 a contacts a color filter 1028 onthose major surfaces and a portion of that image light is absorbed.Preferably, the absorption of the image light 1032 a is selective anddoes not affect the propagation of the in-coupled image light 1032 bthat is also propagating via TIR through the waveguide 1020 b.

With continued reference to FIG. 16 , the color filters 1024 c and 1024b may also be configured as absorption filters. The color filter 1024 cmay be substantially transparent to light of the colors of the imagelight 1032 a, 1032 b such that the image light 1032 a, 1032 b istransmitted through the color filter 1024 c with little to noattenuation, while light of the color of the image light 1032 c isselectively absorbed. Similarly, the color filter 1024 b may besubstantially transparent to light of the color of the image light 1032a such that incident image light 1032 a is transmitted through the colorfilter 1024 b with little to no attenuation, while light of the color ofthe image light 1032 b is selectively absorbed. The color filter 1024 cmay be disposed on a major surface (e.g., the upper major surface) ofthe waveguide 1020 b as shown in FIG. 16 . Alternately, the color filter1024 c may be disposed on a separate substrate positioned between thewaveguides 1020 c and 1020 b. Likewise, the color filter 1024 b may bedisposed on a major surface (e.g., an upper major surface) of thewaveguide 1020 a. Alternately, the color filter 1024 b may be disposedon a separate substrate positioned between the waveguides 1020 b and1020 a. It will be appreciated that the color filters 1024 c and 1024 bmay be vertically aligned with the single-pupil of the projector thatoutputs the image light 1032 a, 1032 b, 1032 c (in orientations wherethe image light 1032 a, 1032 b, 1032 c propagates vertically to thewaveguide stack 1020, as illustrated).

In some embodiments, the color filters 1026 and 1028 may havesingle-pass attenuation factors of less than about 10%, (e.g., less thanor equal to about 5%, less than or equal to about 2%, and greater thanabout 1%) to avoid significant undesired absorption of light propagatingthrough the thickness the waveguides 1020 c, 1020 b (e.g., light of thecolors of the image light 1032 a, 1032 b propagating through thewaveguides 1020 c, 1020 b from the ambient environment and/or otherwaveguides). Various embodiments of the color filters 1024 c and 1024 bmay be configured to have low attenuation factors for the wavelengthsthat are to be transmitted and high attenuation factor for thewavelengths that are to be absorbed. For example, in some embodiments,the color filter 1024 c may be configured to transmit greater than 80%,greater than 90%, or greater than 95%, of incident light having thecolors of the image light 1032 a, 1032 b and absorb greater than 80%,greater than 90%, or greater than 95%, of incident light having thecolor of the image light 1032 a. Similarly, the color filter 1024 b maybe configured to transmit greater than 80%, greater than 90%, or greaterthan 95%, of incident light having the color of the image light 1032 aand absorb greater than 80%, greater than 90%, or greater than 95%, ofincident light having the color of the image light 1032 b.

In some embodiments, the color filters 1026, 1028, 1024 c, 1024 b maycomprise a layer of color selective absorbing material deposited on oneor both surfaces of the waveguide 1020 c, 1020 b and/or 1020 a. Thecolor selective absorbing material may comprise a dye, an ink, or otherlight absorbing material such as metals, semiconductors, anddielectrics. In some embodiments, the absorption of material such asmetals, semiconductors, and dielectrics may be made color selective byutilizing these materials to form subwavelength gratings (e.g., agrating that does not diffract the light). The gratings may be made ofplasmonics (e.g. gold, silver, and aluminum) or semiconductors (e.g.silicon, amorphous silicon, and germanium).

The color selective material may be deposited on the substrate usingvarious deposition methods. For example, the color selective absorbingmaterial may be deposited on the substrate using jet depositiontechnology (e.g., ink-jet deposition). Ink-jet deposition may facilitatedepositing thin layers of the color selective absorbing material.Because ink-jet deposition allows for the deposition to be localized onselected areas of the substrate, ink-jet deposition provides a highdegree of control over the thicknesses and compositions of the layers ofthe color selective absorbing material, including providing fornonuniform thicknesses and/or compositions across the substrate. In someembodiments, the color selective absorbing material deposited usingink-jet deposition may have a thickness between about 10 nm and about 1micron (e.g., between about 10 nm and about 50 nm, between about 25 nmand about 75 nm, between about 40 nm and about 100 nm, between about 80nm and about 300 nm, between about 200 nm and about 500 nm, betweenabout 400 nm and about 800 nm, between about 500 nm and about 1 micron,or any value in a range/sub-range defined by any of these values).Controlling the thickness of the deposited layer of the color selectiveabsorbing material may be advantageous in achieving a color filterhaving a desired attenuation factor. Furthermore, layers havingdifferent thickness may be deposited in different portions of thesubstrate. Additionally, different compositions of the color selectiveabsorbing material may be deposited in different portions of thesubstrate using ink-jet deposition. Such variations in compositionand/or thickness may advantageously allowing for location-specificvariations in absorption. For example, in areas of a waveguide in whichtransmission of light from the ambient (to allow the viewer to see theambient environment) is not necessary, the composition and/or thicknessmay be selected to provide high absorption or attenuation of selectedwavelengths of light. Other deposition methods such as coating,spin-coating, spraying, etc. may be employed to deposit the colorselective absorbing material on the substrate.

FIG. 17 illustrates an example of a top-down view of the waveguideassemblies of FIGS. 15 and 16 . As illustrated, in-coupling opticalelements 1022 a, 1022 b, 1022 c spatially overlap. In addition, thewaveguides 1020 a, 1020 b, 1020 c, along with each waveguide'sassociated light distributing element 730, 740, 750 and associatedout-coupling optical element 800, 810, 820, may be vertically aligned.

The in-coupling optical elements 1022 a, 1022 b, 1022 c are configuredto in-couple incident image light 1032 a, 1032 b, 1032 c (FIGS. 15 and16 ), respectively, in waveguides 1020 a, 1020 b, 1020 c, respectively,such that the image light propagates towards the associated lightdistributing element 730, 740, 750 by TIR.

FIG. 18 illustrates another example of a top-down view of the waveguideassemblies of FIGS. 15 and 16 . As in FIG. 17 , in-coupling opticalelements 1022 a, 1022 b, 1022 c spatially overlap and the waveguides1020 a, 1020 b, 1020 c are vertically aligned. In place of eachwaveguide's associated light distributing element 730, 740, 750 andassociated out-coupling optical element 800, 810, 820, however, arecombined OPE/EPE's 1281, 1282, 1283, respectively. The in-couplingoptical elements 1022 a, 1022 b, 1022 c are configured to in-coupleincident image light 1032 a, 1032 b, 1032 c (FIGS. 15 and 16 ),respectively, in waveguides 1020 a, 1020 b, 1020 c, respectively, suchthat the image light propagates towards the associated combinedOPE/EPE's 1281, 1282, 1283 by TIR.

While FIGS. 15-18 show overlapping in-coupling optical elements for asingle-pupil configuration of the display system, it will be appreciatedthat the display system may have a two-pupil configuration in someembodiments. In such a configuration, where three component colors areutilized, image light for two colors may have overlapping in-couplingoptical elements, while image light for a third color may have alaterally-shifted in-coupling optical element. For example, the opticalcombiner 1050 (FIGS. 11A, 12, 13A-13B) and/or light redirectingstructures 1080 a, 1080 c may be configured to direct image lightthrough the projection optics 1070 such that image light of two colorsare incident on directly overlapping areas of the eyepiece 1020 whileanother color of the image light is incident on an area that islaterally-shifted. For example, the reflective surfaces 1052, 1054 (FIG.11A) may be angled such that image light of one color follows a commonlight path with image light from the emissive micro-display 1030 b,while image light of another color follows a different light path. Insome embodiments, rather than having both light redirecting structures1080 a, 1080 c (FIG. 12 ), one of these light redirecting structures maybe omitted, so that only light from one of the micro-displays 1030 a,1030 c is angled to provide a different light path from the lightemitted by the other two micro-displays.

FIG. 19A illustrates a side view of an example of an eyepiece having astack of waveguides with some overlapping and some laterally-shiftedin-coupling optical elements. The eyepiece of FIG. 19A is similar to theeyepiece of FIG. 15 , except that one of the in-coupling opticalelements is laterally shifted relative to the other in-coping opticalelements. In the illustrated orientation of the eyepiece 1020 in whichthe image light propagates vertically down the page towards the eyepiece1020, the in-coupling optical elements 1022 a, 1022 c are verticallyaligned with each other (e.g., along an axis parallel to the directionof propagation of the image light 1032 a, 1032 c) such that theyspatially overlap with each other as seen in a head-on view in adirection of the image light 1032 a, 1032 c propagating to thein-coupling optical elements 1022 a, 1022 b, 1022 c. As seen in the samehead-on view (e.g., as seen in a top-down view in the illustratedorientation), the in-coupling optical element 1022 b is shiftedlaterally relative to the other in-coupling optical elements 1022 a,1022 c. Light for the in-coupling optical element 1022 b is output tothe eyepiece 1020 through a different exit pupil than light for thein-coupling optical elements 1022 a, 1022 c. It will be appreciated thatthe illustrated waveguide stack comprising the waveguides 1020 a, 1020b, 1020 c may be utilized in place of the single illustrated waveguide1020 a of FIGS. 13 and 14 .

With continued reference to FIG. 19 , the in-coupling optical element1022 c is configured to in-couple the image light 1032 c into thewaveguide 1020 c such that it propagates through the waveguide 1020 c bymultiple total internal reflections between the upper and bottom majorsurfaces of the waveguide 1020 c, the in-coupling optical element 1022 bis configured to in-couple the image light 1032 b into the waveguide1020 b such that it propagates through the waveguide 1020 b by multipletotal internal reflections between the upper and bottom major surfacesof the waveguide 1020 b, and the in-coupling optical element 1022 a isconfigured to in-couple the image light 1032 a into the waveguide 1020 asuch that it propagates through the waveguide 1020 a by multiple totalinternal reflections between the upper and bottom major surfaces of thewaveguide 1020 a.

The in-coupling optical element 1022 c is preferably configured toin-couple all the incident light 1032 c into the associated waveguide1020 c while being transmissive to all the incident light 1032 a. On theother hand, the image light 1032 b may propagate to the in-couplingoptical element 1022 b without needing to propagate through any otherin-coupling optical elements. This may be advantageous in someembodiments by allowing light, to which the eye is more sensitive, to beincident on a desired in-coupling optical element without any loss ordistortion associated with propagation through other in-coupling opticalelements. Without being limited by theory, in some embodiments, theimage light 1032 b is green light, to which the human eye is moresensitive. It will be appreciated that, while the waveguides 1020 a,1020 b, 1020 c are illustrated arranged a particular order, in someembodiments, the order of the waveguides 1020 a, 1020 b, 1020 c maydiffer.

It will be appreciated that, as discussed herein, the in-couplingoptical element 1022 c overlying the in-coupling optical elements 1022 amay not have perfect selectivity. Some of the image light 1032 a mayundesirably be in-coupled into the waveguide 1020 c by the in-couplingoptical element 1022 c; and some of the image light 1032 c may betransmitted through the in-coupling optical element 1022 c, after whichthe image light 1032 c may strike the in-coupling optical element 1020 aand be in-coupled into the waveguide 1020 a. As discussed herein, suchundesired in-coupling may be visible as ghosting or crosstalk.

FIG. 19B illustrates a side view of an example of the eyepiece of FIG.19A with color filters for mitigating ghosting or crosstalk betweenwaveguides. In particular, color filters 1024 c and/or 1026 are added tothe structures shown in FIG. 19A. As illustrated, the in-couplingoptical element 1022 c may unintentionally in-couple a portion of theimage light 1032 a into the waveguide 1020 c. In addition, oralternatively, a portion of the image light 1032 c undesirably betransmitted through the in-coupling optical element 1022 c after whichit may unintentionally be in-coupled by the in-coupling optical element1022 a.

To mitigate unintentionally in-couple image light 1032 a propagatingthrough the waveguide 1022 c, absorptive color filters 1026 may beprovided on one or both major surfaces of the waveguide 1022 c. Theabsorptive color filters 1026 may be configured to absorb light of thecolor of the unintentionally in-coupled image light 1032 a. Asillustrated, the absorptive color filters 1026 are disposed in thegeneral direction of propagation of the image light through thewaveguide 1020 c. Thus, the absorptive color filters 1026 are configuredto absorb image light 1032 a as that light propagates through thewaveguide 1020 c by TIR and contacts the absorptive color filters 1026while reflecting off one or both of the major surfaces of the waveguide1020 c.

With continued reference to FIG. 19B, to mitigate image light 1032 cwhich propagates through the in-coupling optical element 1022 c withoutbeing in-coupled, the absorptive color filter 1024 c may be providedforward of the in-coupling optical element 1022 a. The absorptive colorfilter 1024 c is configured to absorb light of the color of the imagelight 1032 c, to prevent that light from propagating to the in-couplingoptical element 1022 a. While illustrated between the waveguides 1020 cand 1020 b, in some other embodiments, the absorptive color filter 1024c may be disposed between the waveguides 1020 b and 1020 a. It will beappreciated that further details regarding the composition, formation,and properties of the absorptive color filters 1024 c and 1026 areprovided in the discussion of FIG. 16 .

It will also be appreciated that in the embodiments illustrated in FIGS.16 and 19B, one or more of the color filters 1026, 1028, 1024 c, and1024 b may be omitted if one or more in-coupling optical elements 1022a, 1022 b, 1022 c have sufficiently high selectivity for the color ofthe light that is intended to be in-coupled into the associatedwaveguide 1020 a, 1020 b, 1022 c, respectively.

FIG. 20A illustrates an example of a top-down view of the eyepieces ofFIGS. 19A and 19B. As illustrated, in-coupling optical elements 1022 a,1022 c spatially overlap, while in-coupling optical element 1022 b islaterally-shifted. In addition, the waveguides 1020 a, 1020 b, 1020 c,along with each waveguide's associated light distributing element 730,740, 750 and associated out-coupling optical element 800, 810, 820, maybe vertically aligned. The in-coupling optical elements 1022 a, 1022 b,1022 c are configured to in-couple incident image light 1032 a, 1032 b,1032 c (FIGS. 15 and 16 ), respectively, in waveguides 1020 a, 1020 b,1020 c, respectively, such that the image light propagates towards theassociated light distributing element 730, 740, 750 by TIR.

FIG. 20B illustrates another example of a top-down view of the waveguideassembly of FIGS. 19A and 19B. As in FIG. 20A, in-coupling opticalelements 1022 a, 1022 c spatially overlap, the in-coupling opticalelement is laterally-shifted, and the waveguides 1020 a, 1020 b, 1020 care vertically aligned. In place of each waveguide's associated lightdistributing element 730, 740, 750 and associated out-coupling opticalelement 800, 810, 820, however, are combined OPE/EPE's 1281, 1282, 1283,respectively. The in-coupling optical elements 1022 a, 1022 b, 1022 care configured to in-couple incident image light 1032 a, 1032 b, 1032 c(FIGS. 15 and 16 ), respectively, in waveguides 1020 a, 1020 b, 1020 c,respectively, such that the image light propagates towards theassociated combined OPE/EPE's 1281, 1282, 1283 by TIR.

With reference now to FIG. 21 , it will be appreciated that re-bounce ofin-coupled light may undesirably occur in waveguides. Re-bounce occurswhen in-coupled light propagating along a waveguide strikes thein-coupling optical element a second or subsequent time after theinitial in-coupling incidence. Re-bounce may result in a portion of thein-coupled light being undesirably out-coupled and/or absorbed by amaterial of the in-coupling optical element. The out-coupling and/orlight absorption undesirably may cause a reduction in overallin-coupling efficiency and/or uniformity of the in-coupled light.

FIG. 21 illustrates a side view of an example of re-bounce in awaveguide 1030 a. As illustrated, image light 1032 a is in-coupled intothe waveguide 1030 a by in-coupling optical element 1022 a. In-couplingoptical element 1022 a redirects the image light 1032 a such that itgenerally propagates through the waveguide in the direction 1033.Re-bounce may occur when in-coupled image light internally reflects orbounces off a major surface of the waveguide 1030 a opposite thein-coupling optical element 1022 a and is incident on or experiences asecond bounce (a re-bounce) at the in-coupling optical element 1022 a.The distance between two neighboring bounces on the same surface of thewaveguide 1030 a is indicated by spacing 1034.

Without being limited by theory, it will be appreciated that thein-coupling optical element 1022 a may behave symmetrically; that is, itmay redirect incident light such that the incident light propagatesthrough the waveguide at TIR angles. However, light that is incident onthe diffractive optical elements at TIR angles (such as upon re-bounce)may also be out-coupled. In addition or alternatively, in embodimentswhere the in-coupling optical element 1022 a is coated with a reflectivematerial, it will be understood that the reflection of light off of alayer of material such as metal may also involve partial absorption ofthe incident light, since reflection may involve the absorption andemission of light from a material. As a result, light out-couplingand/or absorption may undesirably cause loss of in-coupled light.Accordingly, re-bounced light may incur significant losses, as comparedwith light that interacts only once with the in-coupling optical element1022 a.

In some embodiments, the in-coupling elements are configured to mitigatein-coupled image light loss due to re-bounce. Generally, re-bounce ofin-coupled light occurs towards the end 1023 of the in-coupling opticalelement 1022 a in the propagation direction 1033 of the in-coupledlight. For example, light in-coupled at the end of the in-couplingoptical element 1022 a opposite the end 1023 may re-bounce if thespacing 1034 for that light is sufficiently short. To avoid suchre-bounce, in some embodiments, the in-coupling optical element 1022 ais truncated at the propagation direction end 1023, to reduce the width1022 w of the in-coupling optical element 1022 a along which re-bounceis likely to occur. In some embodiments, the truncation may be acomplete truncation of all structures of the in-coupling optical element1022 a (e.g., the metallization and diffractive gratings). In some otherembodiments, for example, where the in-coupling optical element 1022 acomprises a metalized diffraction grating, a portion of the in-couplingoptical element 1022 a at the propagation direction end 1023 may not bemetalized, such that the propagation direction end 1023 of thein-coupling optical element 1022 a absorbs less re-bouncing light and/oroutcouples re-bouncing light with a lower efficiency. In someembodiments, a diffractive region of an in-coupling optical element 1022a may have a width along a propagation direction 1033 shorter than itslength perpendicular to the propagation direction 1033, and/or may besized and shaped such that a first portion of image light 1032 a isincident on the in-coupling optical element 1022 a and a second portionof the beam of light impinges on the waveguide 1030 a without beingincident on the in-coupling optical element 1022 a. While waveguide 1032a and light in-coupling optical element 1022 a are illustrated alone forclarity, it will be appreciated that re-bounce and the strategiesdiscussed for reducing re-bounce may apply to any of the in-couplingoptical elements disclosed herein. It will also be appreciated that thespacing 1034 is related to the thickness of the waveguide 1030 a (alarger thickness results in a larger spacing 1034). In some embodiments,the thickness of individual waveguides may be selected to set thespacing 1034 such that re-bounce does not occur. Further detailsregarding re-bounce mitigation may be found in U.S. ProvisionalApplication No. 62/702,707, filed on Jul. 24, 2018, the entiredisclosure of which is incorporated by reference herein.

FIGS. 22A-23C illustrate examples of top-down views of an eyepiecehaving in-coupling optical elements configured to reduce re-bounce.In-coupling optical element 1022 a, 1022 b, 1022 c are configured toin-couple light such that it propagates in a propagation directiontowards the associated light distributing elements 730, 740, 750 (FIGS.22A-22C) or combined OPE/EPE's 1281, 1282, 1283 (FIGS. 23A-23C). Asillustrated, the in-coupling optical element 1022 a, 1022 b, 1022 c mayhave a shorter dimension along the propagation direction and a longerdimension along the transverse axis. For example, the in-couplingoptical element 1022 a, 1022 b, 1022 c may each be in the shape of arectangle with a shorter side along the axis of the propagationdirection and a longer side along an orthogonal axis. It will beappreciated that the in-coupling optical elements 1022 a, 1022 b, 1022 cmay have other shapes (e.g., orthogonal, hexagonal, etc.). In addition,different ones of the in-coupling optical elements 1022 a, 1022 b, 1022c may have different shapes in some embodiments. Also, preferably, asillustrated, non-overlapping in-coupling optical elements may bepositioned such that they are not in the propagation direction of otherin-coupling optical elements. For example, as shown in FIGS. 22A, 22B,23A, and 23B, the non-overlapping in-coupling optical elements may bearranged in a line along an axis crossing (e.g., orthogonal to) the axisof the propagation direction.

It will be appreciated that in the waveguide assemblies of FIGS. 22A-22Care similar, except for the overlap of the in-coupling optical elements1022 a, 1022 b, 1022 c. For example, FIG. 22A illustrates in-couplingoptical elements 1022 a, 1022 b, 1022 c with no overlap. FIG. 22Billustrates overlapping in-coupling optical elements 1022 a, 1022 c, andnon-overlapping in-coupling optical elements 1022 b. FIG. 22Cillustrates overlap between all the in-coupling optical elements 1022 a,1022 b, 1022 c.

The waveguide assemblies of FIGS. 23A-23C are also similar, except forthe overlap of the in-coupling optical elements 1022 a, 1022 b, 1022 c.FIG. 23A illustrates in-coupling optical elements 1022 a, 1022 b, 1022 cwith no overlap. FIG. 23B illustrates overlapping in-coupling opticalelements 1022 a, 1022 c, and non-overlapping in-coupling opticalelements 1022 b. FIG. 22C illustrates overlap between all thein-coupling optical elements 1022 a, 1022 b, 1022 c.

With reference now to FIG. 24A, it will be appreciated that the emissivemicro-displays have high etendue, which presents a challenge forefficient light utilization. As discussed herein, the emissivemicro-displays may include a plurality of individual light emitters.Each of these light emitters may have a large angular emission profile,e.g., a Lambertian or near-Lambertian emission profile. Undesirably, notall of this light may be captured and directed to the eyepiece of thedisplay system.

FIG. 24A illustrates an example of angular emission profiles of lightemitted by individual light emitters 1044 of an emissive micro-display1032, and light captured by projection optics 1070. The illustratedemissive micro-display 1032 may correspond to any of theemissive-micro-displays disclosed herein, including the emissivemicro-displays 1032 a, 1032 b, 1032 c. As illustrated, the projectionoptics 1070 may be sized such that it will capture light having anangular emission profile 1046. However, the angular emission profiles1046 in the light emitters 1044 is significantly larger; not all of thelight emitted by the light emitters 1044 will be incident on theprojection optics 1070, nor necessarily incident at angles at which thelight will propagate into and through the projection optics 1070. As aresult, some of the light emitted by the light emitter 1044 mayundesirably be “wasted” since it is not captured and ultimately relayedto the user's eye to form images. This may result in images that appeardarker than would be expected if more of the light outputted by thelight emitters 1040 ultimately reached the user's eye.

In some embodiments, one strategy for capturing more of the lightemitted by the light emitters 1040 is to increase the size of theprojection optics 1070, to increase the size of the numerical apertureof the projection optics 1070 capturing light. In addition oralternatively, the projection optics 1070 may also be formed with highrefractive index materials (e.g., having refractive indices above 1.5)which may also facilitate light collection. In some embodiments, theprojection optics 1070 may utilize a lens sized to capture a desired,high proportion of the light emitted by the light emitters 1044. In someembodiments, the projection optics 1070 may be configured to have anelongated exit pupil, e.g., to emit light beams having a cross-sectionalprofile similar to the shapes of the in-coupling optical elements 1022a, 1022 b, 1022 c of FIGS. 22A-23C. For example, the projection optics1070 may be elongated in a dimension corresponding to the elongateddimension of the in-coupling optical elements 1022 a, 1022 b, 1022 c ofFIGS. 22A-23C. Without being limited by theory, such elongatedin-coupling optical elements 1022 a, 1022 b, 1022 c may improve theetendue mismatch between the emissive micro-display and the eyepiece1020 (FIGS. 22A-23C). In some embodiments, the thickness of thewaveguides of the eyepiece 1020 (e.g., FIGS. 11A, and 12-23C) may beselected to increase the percentage of light effectively captured, e.g.,by reducing re-bounce by increasing the re-bounce spacing, as discussedherein.

In some embodiments, one or more light collimators may be utilized toreduce or narrow the angular emission profile of light from the lightemitters 1044. As a result, more of the light emitted by the lightemitters 1044 may be captured by the projection optics 1070 and relayedto the eyes of a user, advantageously increasing the brightness ofimages and the efficiency of the display system. In some embodiments,the light collimators may allow the light collection efficiency of theprojection optics (the percentage of light emitted by the light emitters1044 that is captured by the projection optics) to reach values of 80%or more, 85% or more, or 90% or more, including about 85-95% or 85-90%.In addition, the angular emission profile of the light from the lightemitters 1044 may be reduced to 60° or less, 50° or less, or 40° or less(from, e.g., 180°). In some embodiments, the reduced angular emissionprofiles may be in the range of about 30-60°, 30-50°, or 30-40°. It willbe appreciated that light from the light emitters 1044 may make out theshape of a cone, with the light emitter 1044 at the vertex of the cone.The angular mission profile refers to the angle made out by the sides ofthe cone, with the associated light emitter 1044 at the vertex of theangle (as seen in a cross-section taken along a plane extending throughthe middle of the cone and including the cone apex).

FIG. 24B illustrates an example of the narrowing of angular emissionprofiles using an array of light collimators. As illustrated, theemissive micro-display 1032 includes an array of light emitters 1044,which emit light with an angular emission profile 1046. An array 1300 oflight collimators 1302 is disposed forward of the light emitters 1044.In some embodiments, each light emitter 1044 is matched 1-to-1 with anassociated light collimator 1302 (one light collimator 1302 per lightemitter 1044). Each light collimator 1302 redirects incident light fromthe associated light emitter 1044 to provide a narrowed angular emissionprofiles 1047. Thus, the relatively large angular emission profiles 1046are narrowed to the smaller angular emission profiles 1047.

In some embodiments, the light collimators 1302 and array 1300 may bepart of the light redirecting structures 1080 a, 180 c of FIGS. 12 and13A. Thus, light collimators 1302 may narrow the angular emissionprofile of the light emitters 1044 and also redirect the light such thatit propagates into the optical combiner 1050 at the appropriate anglesto define multiple light paths and the related multiple exit pupils. Itwill be appreciated that light may be redirected in particulardirections by appropriately shaping the light collimators 1302.

Preferably, the light collimators 1302 are positioned in tight proximityto the light emitters 1044 to capture a large proportion of the lightoutputted by the light emitters 1044. In some embodiments, there may bea gap between the light collimators 1302 and the light emitters 1044. Insome other embodiments, the light collimator 1302 may be in contact withthe light emitters 1044. It will be appreciated that the angularemission profile 1046 may make out a wide cone of light. Preferably, theentirety or majority of a cone of light from a light emitter 1044 isincident on a single associated light collimator 1302. Thus, in someembodiments, each light emitter 1044 is smaller (occupies a smallerarea) than the light receiving face of an associated light collimator1302. In some embodiments, each light emitter 1044 has a smaller widththan the spacing between neighboring far light emitters 1044.

Advantageously, the light collimators 1302 may increase the efficiencyof the utilization of light and may also reduce the occurrence ofcrosstalk between neighboring light emitters 1044. It will beappreciated that crosstalk between light emitters 1044 may occur whenlight from a neighboring light emitter is captured by a light collimator1302 not associated with that neighboring light emitter. That capturedlight may be propagated to the user's eye, thereby providing erroneousimage information for a given pixel.

With reference to FIGS. 24A and 24B, the size of the beam of lightcaptured by the projection optics 1070 may influence the size of thebeam of light which exits the projection optics 1070. As shown in FIG.24A, without the use light collimators, the exit beam may have arelatively large width 1050. As shown in FIG. 24B, with lightcollimators 1302, the exit beam may have a smaller width 1052. Thus, insome embodiments, the light collimators 1302 may be used to provide adesired beam size for in-coupling into an eyepiece. For example, theamount that the light collimators 1302 narrow the angular emissionprofile 1046 may be selected based at least partly upon the size of theintra-coupling optical elements in the eyepiece to which the lightoutputted by the projection optics 1070 is directed.

It will be appreciated that the light collimators 1302 may take variousforms. For example, the light collimators 1302 may be micro-lenses orlenslets, in some embodiments. As discussed herein, each micro-lenspreferably has a width greater than the width of an associated lightemitter 1044. The micro-lenses may be formed of curved transparentmaterial, such as glass or polymers, including photoresist and resinssuch as epoxy. In some embodiments, light collimators 1302 may benano-lenses, e.g., diffractive optical gratings. In some embodiments,light collimators 1302 may be metasurfaces and/or liquid crystalgratings. In some embodiments, light collimator's 1302 may take the formof reflective wells.

It will be appreciated that different light collimators 1302 may havedifferent dimensions and/or shapes depending upon the wavelengths orcolors of light emitted by the associated light emitter 1044. Thus, forfull-color emissive micro-displays, the array 1300 may include aplurality of light collimators 1302 with different dimensions and/orshapes depending upon the color of light emitted by the associate lightemitter 1044. In embodiments where the emissive micro-display is amonochrome micro-display, the array 1300 may be simplified, with each ofthe light collimators 1302 in the array being configured to redirectlight of the same color. With such monochrome micro-displays, the lightcollimator 1302 may be similar across the array 1300 in someembodiments.

With continued reference to FIG. 24B, as discussed herein, the lightcollimators 1302 may have a 1-to-1 association with the light emitters1044. For example, each light emitter 1044 may have a discreteassociated light collimator 1302. In some other embodiments, lightcollimators 1302 may be elongated such that they extend across multiplelight emitters 1044. For example, in some embodiments, the lightcollimator 1302 may be elongated into the page and extend in front of arow of multiple light emitters 1044. In some other embodiments, a singlelight collimator 1302 may extend across a column of light emitters 1044.In yet other embodiments, the light collimator 1302 may comprise stackedcolumns and/or rows of lens structures (e.g., nano-lens structures,micro-lens structures, etc.).

As noted above, the light collimators 1302 may take the form ofreflective wells. FIG. 25A illustrates an example of a side view of anarray of tapered reflective wells for directing light to projectionoptics. As illustrated, the light collimator array 1300 may include asubstrate 1301 in which a plurality of light collimators 1302, in theform of reflective wells, may be formed. Each well may include at leastone light emitter 1044, which may emit light with a Lambertian angularemission profile 1046. The reflective walls 1303 of the wells of thelight collimators 1302 are tapered and reflect the emitted light suchthat it is outputted from the well with a narrower angular emissionprofile 1047. As illustrated, reflective walls 1303 may be tapered suchthat the cross-sectional size increases with distance from the lightemitter 1044. In some embodiments, the reflective walls 1303 may becurved. For example, the sides 1303 may have the shape of a compoundparabolic concentrator (CPC).

With reference now to FIG. 25B, an example of a side view of anasymmetric tapered reflective well is illustrated. As discussed herein,e.g., as illustrated in FIGS. 12A-13A, it may be desirable to utilizethe light collimators 1302 to steer light in a particular direction notnormal to the surface of the light emitter 1044. In some embodiments, asviewed in a side view such as illustrated in FIG. 25B, the lightcollimator 1302 may be asymmetric, with the upper side 1303 a forming adifferent angle (e.g., a larger angle) with the surface of the lightemitter 1044 than the lower side 1303 b; for example, the angles of thereflective walls 1303 a, 1303 b relative to the light emitter 1044 maydiffer on different sides of the light collimators 1302 in order todirect the light in the particular non-normal direction. Thus, asillustrated, light exiting the light collimator 1302 may propagategenerally in a direction 1048 which is not normal to the surface of thelight emitter 1044. In some other embodiments, in order to direct lightin the direction 1048, the taper of the upper side 1303 a may bedifferent than the taper of the lower side; for example, the upper side1303 a may flare out to a greater extent than the lower side 1303 b.

With continued reference to FIG. 25 , the substrate 1301 may be formedof various materials having sufficient mechanical integrity to maintainthe desired shape of the reflective walls 1303. Examples of suitablematerials include metals, plastics, and glasses. In some embodiments,the substrate 1301 may be a plate of material. In some embodiments,substrate 1301 is a continuous, unitary piece of material. In some otherembodiments, the substrate 1301 may be formed by joining together two ormore pieces of material.

The reflective walls 1303 may be formed in the substrate 1301 by variousmethods. For example, the walls 1303 may be formed in a desired shape bymachining the substrate 1301, or otherwise removing material to definethe walls 1303. In some other embodiments, the walls 1303 may be formedas the substrate 1301 is formed. For example, the walls 1303 may bemolded into the substrate 1301 as the substrate 1301 is molded into itsdesired shape. In some other embodiments, the walls 1303 may be definedby rearrangement of material after formation of the body 2200. Forexample, the walls 1303 may be defined by imprinting.

Once the contours of the walls 1303 are formed, they may undergo furtherprocessing to form surfaces having the desired degree of reflection. Insome embodiments, the surface of the substrate 1301 may itself bereflective, e.g., where the body is formed of a reflective metal. Insuch cases, the further processing may include smoothing or polishingthe interior surfaces of the walls 1303 to increase their reflectivity.In some other embodiments, the interior surfaces of the reflectors 2110may be lined with a reflective coating, e.g., by a vapor depositionprocess. For example, the reflective layer may be formed by physicalvapor deposition (PVD) or chemical vapor deposition (CVD).

It will be appreciated that the location of a light emitter relative toan associated light collimator may influence the direction of emittedlight out of the light collimator. This is illustrated, for example, inFIGS. 26A-26C, which illustrate examples of differences in light pathsfor light emitters at different positions relative to center lines ofoverlying, associated light collimators. As shown in FIG. 26A, theemissive micro-display another 30 has a plurality of light emitters 1044a, each having an associated light collimator 1302 which facilitates theoutput of light having narrowed angular emission profiles 1047. Thelight passes through the projection optics 1070 (represented as a simplelens for ease of illustration), which converges the light from thevarious light emitters 1044 a onto an area 1402 a.

With continued reference to FIG. 26A, in some embodiments, each of thelight collimators 1302 may be symmetric and may have a center line whichextends along the axis of symmetry of the light collimator. In theillustrated configuration, the light emitters 1044 a are disposed on thecenter line of each of the light collimators 1302.

With reference now to FIG. 26B, light emitters 1044 b are offset by adistance 1400 from the center lines of their respective lightcollimators 1302. This offset causes light from the light emitters 1044b to take a different path through the light collimators 1302, whichoutput light from the light emitters 1044 b with narrowed angularemission profiles 1047 b. The projection optics 1070 then converges thelight from the light emitters 1044 b onto the area 1402 b, which isoffset relative to the area 1402 a on which light from the lightemitters 1044 a converge.

With reference now to FIG. 26C, light emitters 1044 c offset from boththe light emitters 1044 a and 1044 b are illustrated. This offset causeslight from the light emitters 1044 c to take a different path throughthe light collimators 1302 than light from the light emitters 1044 a and1044 b. This causes the light collimators 1302 to output light from thelight emitters 1044 c with narrowed angular emission profiles that takea different path to the projection optics 1070 than the light from thelight emitters 1044 a and 1044 b. Ultimately, the projection optics 1070converges the light from the light emitters 1044 c onto the area 1402 c,which is offset relative to the areas 1402 a and 1402 b.

With reference to FIGS. 26A-26C, each triad of light emitters 1044 a,1044 b, 1044 c may share a common light collimator 1302. In someembodiments, the micro-display 1030 may be a full-color micro-displayand each light emitter 1044 a, 1044 b, 1044 c may be configured to emitlight of a different component color. Advantageously, the offset areas1402 a, 1402 b, 1402 c may correspond to the in-coupling opticalelements of a waveguide in some embodiments. For example, the areas 1402a, 1402 b, 1402 c may correspond to the in-coupling optical element 1022a, 1022 b, 1022 c, respectively, of FIGS. 11A and 12 . Thus, the lightcollimators 1302 and the offset orientations of the light emitters 1044a, 1044 b, 1044 c may provide an advantageously simple three-pupilprojection system 1010 using a full-color emissive micro-display.

As noted herein, the light collimator 1302 may also take the form of anano-lens. FIG. 27 illustrates an example of a side view of individuallight emitters 1044 of an emissive micro-display 1030 with an overlyingarray 1300 of light collimators 1302 which are nano-lenses. As discussedherein, individual ones of the light emitters 1044 may each have anassociated light collimator 1302. The light collimators 1302 redirectlight from the light emitters 1044 to narrow the large angular emissionprofile 1046 of the light emitters 1044, to output light with thenarrowed angular emission profile 1047.

With continued reference to FIG. 27 , in some embodiments, the lightcollimators 1302 may be grating structures. In some embodiments, thelight collimators 1302 may be gratings formed by alternating elongateddiscrete expanses (e.g., lines) of material having different refractiveindices. For example, expanses of material 1306 may be elongated intoand out of the page and may be formed in and separated by material ofthe substrate 1308. In some embodiments, the elongated expanses ofmaterial 1306 may have sub-wavelength widths and pitch (e.g., widths andpitch that are smaller than the wavelengths of light that the lightcollimators 1302 are configured to receive from the associated lightemitters 1044). In some embodiments, the pitch 1304 may be 30-300 nm,the depth of the grating may be 10-1000 nm, the refractive index of thematerial forming the substrate 1308 may be 1.5-3.5, and the refractiveindex of the material forming the grating features 1306 may be 1.5-2.5(and different from the refractive index of the material forming thesubstrate 1308).

The illustrated grating structure may be formed by various methods. Forexample, the substrate 1308 may be etched or nano-imprinted to definetrenches, and the trenches may be filled with material of a differentrefractive index from the substrate 1308 to form the grating features1306.

Advantageously, nano-lens arrays may provide various benefits. Forexample, the light collection efficiencies of the nano-lenslets may belarge, e.g., 80-95%, including 85-90%, with excellent reductions inangular emission profiles, e.g., reductions to 30-40° (from 180°). Inaddition, low levels of cross-talk may be achieved, since each of thenano-lens light collimators 1302 may have physical dimensions andproperties (e.g., pitch, depth, the refractive indices of materialsforming the feature 1306 and substrate 1308) selected to act on light ofparticular colors and possibly particular angles of incidence, whilepreferably providing high extinction ratios (for wavelengths of light ofother colors). In addition, the nano-lens arrays may have flat profiles(e.g., be formed on a flat substrate), which may facilitates integrationwith micro-displays that may be flat panels, and may also facilitatemanufacturing and provide high reproducibility and precision in formingthe nano-lens array. For example, highly reproducible trench formationand deposition processes may be used to form each nano-lens. Moreover,these processes allow, with greater ease and reproducibility, forvariations between nano-lenses of an array than are typically achievedwhen forming curved lens with similar variations.

With reference now to FIG. 28 , a perspective view of an example of anemissive micro-display 1030 is illustrated. It will be appreciated thatthe light collimator arrays 1300 advantageously allow light emitted froma micro-display to be routed as desired. As result, in some embodiments,the light emitters of a full-color micro-display may be organized asdesired, e.g., for ease of manufacturing or implementation in thedisplay device. In some embodiments, the light emitters 1044 may bearranged in rows or columns 1306 a, 1306 b, 1306 c. Each row or columnmay include light emitters 1044 configured to emit light of the samecomponent color. In displays where three component colors are utilized,there may be groups of three rows or columns which repeat across themicro-display 1030. It will be appreciated that where more componentcolors are utilized, each repeating group may have that number of rowsor columns. For example, where four component colors are utilized, eachgroup may have four rows or four columns, with one row or one columnformed by light emitters configured to emit light of a single componentcolor.

In some embodiments, some rows or columns may be repeated to increasethe number of light emitters of a particular component color. Forexample, light emitters of some component colors may occupy multiplerows or columns. This may facilitate color balancing and/or may beutilized to address differential aging or reductions in light emissionintensity over time.

With reference to FIGS. 27 and 28 , in some embodiments, the lightemitters 1044 may each have an associated light collimator 1302. In someother embodiments, each line 1306 a, 1306 b, 1306 c of multiple lightemitters 1044 may have a single associated light collimator 1302. Thatsingle associated light collimator 1302 may extend across substantiallythe entirety of the associated line 1306 a, 1306 b, or 1306 c. In someother embodiments, the associated light collimator 1302 may be elongatedand extend over a plurality of light emitters 1044 forming a portion ofan associated line 1306 a, 1306 b, or 1306 c, and multiple similar lightcollimators 1302 may be provided along each of the associated lines 1306a, 1306 b, 1306 c.

With continued reference to FIG. 28 , each light emitter 1044 may beelongated along a particular axis (e.g., along the y-axis asillustrated); that is, each light emitter has a length along theparticular axis, the length being longer than a width of the lightemitter. In addition, a set of light emitters configured to emit lightof the same component color may be arranged in a line 1306 a, 1306 b, or1306 c (e.g. a row or column) extending along an axis (e.g., the x-axis)which crosses (e.g., is orthogonal to) the light emitter 1044's elongateaxis. Thus, in some embodiments, light emitters 1044 of the samecomponent color form a line 1306 a, 1306 b, or 1306 c of light emitters,with the line extending along a first axis (e.g., the x-axis), and withindividual light emitters 1044 within the line elongated along a secondaxis (e.g., the y-axis).

In contrast, it will be appreciated that full-color micro-displaytypically include sub-pixels of each component color, with thesub-pixels arranged in particular relatively closely-packed spatialorientations in groups, with these groups reproduced across an array.Each group of sub-pixels may form a pixel in an image. In some cases,the sub-pixels are elongated along an axis, and rows or columns ofsub-pixels of the same component color extent along that same axis. Itwill be appreciated that such an arrangement allows the sub-pixels ofeach group to be located close together, which may have benefits forimage quality and pixel density. In the illustrated arrangement of FIG.28 , however, sub-pixels of different component colors are relativelyfar apart, due to the elongate shape of the light emitters 1044; thatis, the light emitters of the line 1306 a are relatively far apart fromthe light emitters of the line 1306 c since the elongated shape of thelight emitters of the line 1306 b causes the light emitters 1306 a and1306 c to be spaced out more than neighboring light emitters of a givenline of light emitters. While this may be expected to provideunacceptably poor image quality if the image formed on the surface ofthe micro-display 1030 was directly relayed to a user's eye, the use ofthe light collimator array 1300 advantageously allows light of differentcolors to be routed as desired to form a high quality image. Forexample, light of each component color may be used to form separatemonochrome images which are then routed to and combined in an eyepiece,such as the eyepiece 1020 (e.g., FIGS. 11A and 12-14 ).

With reference to FIGS. 27 and 28 , in some embodiments, the lightemitters 1044 may each have an associated light collimator 1302. In someother embodiments, each line 1306 a, 1306 b, 1306 c of light emitters1044 may have a single associated light collimator 1302. That singleassociated light collimator 1302 may extend across substantially theentirety of the associated line 1306 a, 1306 b, or 1306 c. In some otherembodiments, the associated light collimator 1302 may be elongated andextend over a plurality of light emitters 1044 forming a portion of anassociated line 1306 a, 1306 b, or 1306 c, and multiple similar lightcollimators 1302 may be provided along each of the associated lines 1306a, 1306 b, 1306 c.

It will be appreciated that the light collimators 1302 may be utilizedto direct light along different light paths to form multi-pupilprojections systems. For example, the light collimators 1302 may directlight of different component colors to two or three areas, respectively,for light in-coupling.

FIG. 29 illustrates an example of a wearable display system with thefull-color emissive micro-display 1030 of FIG. 28 used to form amulti-pupil projection system 1010. In the illustrated embodiment, thefull-color emissive micro-display 1030 emits light of three componentcolors and forms a three-pupil projection system 1010. The projectionsystem 1010 has three exit pupils through which image light 1032 a, 1032b, 1032 c of different component colors propagates to threelaterally-shifted light in-coupling optical elements 1022 a, 1022 b,1022 c, respectively, of an eyepiece 1020. The eyepiece 1020 then relaysthe image light 1032 a, 1032 b, 1032 c to the eye 210 of a user.

The emissive-micro-display 1030 includes an array of light emitters1044, which may be subdivided into monochrome light emitters 1044 a,1044 b, 1044 c, which emit the image light 1032 a, 1032 b, 1032 c,respectively. It will be appreciated that the light emitters 1044 emitimage light with a broad angular emission profile 1046. The image lightpropagates through the array 1300 of light collimators, which reducesthe angular emission profile to the narrowed angular emission profile1047.

In addition, the array of 1300 of light collimators is configured toredirect the image light (image light 1032 a, 1032 b, 1032 c) such thatthe image light is incident on the projection optics 1070 at angleswhich cause the projection optics 1070 to output the image light suchthat the image light propagates to the appropriate in-coupling opticalelement 1022 a, 1022 b, 1022 c. For example, the 1300 array of lightcollimators is preferably configured to: direct the image light 1032 asuch that it propagates through the projection optics 1070 and isincident on the in-coupling optical element 1022 a; direct the imagelight 1032 b such that it propagates through the projection optics 1070and is incident on the in-coupling optical element 1022 b; and directthe image light 1032 c such that it propagates through the projectionoptics 1070 and is incident on the in-coupling optical element 1022 c.

Since different light emitters 1044 may emit light of differentwavelengths and may need to be redirected into different directions toreach the appropriate in-coupling optical element, in some embodiments,the light collimators associated with different light emitters 1044 mayhave different physical parameters (e.g., different pitches, differentwidths, etc.). Advantageously, the use of flat nano-lenses as lightcollimators facilitates the formation of light collimators which vary inphysical properties across the array 1300 of light collimators. As notedherein, the nano-lenses may be formed using patterning and depositionprocesses, which facilitates the formation of structures with differentpitches, widths, etc. across a substrate.

With reference again to FIG. 24A, it will be appreciated that theillustrated display system shows a single emissive micro-display andomits an optical combiner 1050 (FIGS. 11A and 12-13B). In embodimentsutilizing an optical combiner 1050, the reflective surfaces 1052, 1054(FIGS. 11A, 12-13B, and 30B) in the optical combiner 1050 are preferablyspecular reflectors, and light from the light emitters 1044 would beexpected to retain their large angular emission profiles after beingreflected from the reflective surfaces 1052, 1054. Thus, the problemswith wasted light shown in FIG. 24A are similarly present when anoptical combiner 1050 is utilized.

With reference now to FIG. 30A, an example of a wearable display systemwith an emissive micro-display and an associated array of lightcollimators is illustrated. FIG. 30A shows additional details regardingthe interplay between the light emitters 1044, the light collimators1302, and the in-coupling optical elements of the eyepiece 1020. Thedisplay system includes a micro-display 1030 b, which may be afull-color micro-display in some embodiments. In some other embodiments,the micro-display 1030 b may be a monochrome micro-display andadditional monochrome micro-displays (not shown) may be provided atdifferent faces of the optional optical combiner 1050 (as shown in FIG.30C).

With continued reference to FIG. 30A, the micro-display 1030 b includesan array of light emitters 1044, each of which emits light with a wideangular emission profile (e.g., a Lambertian angular emission profile).Each light emitter 1044 has an associated, dedicated light collimator1302 which effectively narrows the angular emission profile to anarrowed angular remission profile 1047. Light beams 1032 b with thenarrowed angular emission profiles pass through the projection optics1070, which projects or converges those light beams onto the in-couplingoptical element 1022 b. It will be appreciated that the light beams 1032b have a certain cross-sectional shape and size 1047 a. In someembodiments, the in-coupling optical element 1022 b has a size and shapewhich substantially matches or is larger than the cross-sectional shapeand size of the light beam 1032 b, when that beam 1032 b is incident onthat in-coupling optical element 1022 b. Thus, in some embodiments, thesize and shape of the in-coupling optical element 1022 b may be selectedbased upon the cross-sectional size and shape of the light beam 1032 bwhen incident on the in-coupling optical element 1022 b. In some otherembodiments, other factors (re-bounce mitigation, or the angles or fieldof view supported by the in-coupling optical elements 1022 b) may beutilized to determine the size and shape of the in-coupling opticalelement 1022 b, and the light collimator 1302 may be configured (e.g.,sized and shaped) to provide the light beam 1032 b with an appropriatelysized and shaped cross-section, which is preferably fully or nearlyfully encompassed by the size and shape of the in-coupling opticalelement 1022 b. In some embodiments, physical parameters for the lightcollimator 1302 and the in-coupling optical element 1022 b may bemutually modified to provide highly efficient light utilization inconjunction with other desired functionality (e.g., re-bouncemitigation, support for the desired fields of view, etc.).Advantageously, the above-noted light collimation provided by the lightcollimator 1302, and matching of the cross-sectional size and shape ofthe light beam 1032 b with the size and shape of the in-coupling opticalelement 1022 b allows the in-coupling optical element 1022 b to capturea large percentage of the incident light beam 1032 b. The in-coupledlight then propagates through the waveguide 1020 b and is out-coupled tothe eye 210.

As illustrated, the micro-display 1030 b may include an array 1042 oflight emitters 1044, each surrounded by non-light-emitting areas 1045having a total width 1045 w. In addition, the light emitters 1044 have awidth W and a pitch P. In arrays in which the light emitters 1044 areregularly spaced, each light emitter 1044 and surrounding area 1045effectively forms a unit cell having the width 1045 w, which may beequal to the pitch P.

In some embodiments, the light collimators 1302 are micro-lensesdisposed directly on and surrounding associated light emitters 1044. Insome embodiments, the width of the micro-lenses 1302 is equal to 1045 w,such that neighboring micro-lenses 1302 nearly contact or directlycontact one another. It will be appreciated that light from the lightemitters 1044 may fill the associated micro-lens 1302, effectivelymagnifying the area encompassed by the light emitter 1044.Advantageously, such a configuration reduces the perceptibility of theareas 1045 which do not emit light and may otherwise be visible as darkspaces to a user. However, because micro-lens 1302 effectively magnifiesthe associated light emitter 1044 such that it extends across the entirearea of the micro-lens 1302, the areas 1045 may be masked.

With continued reference to FIG. 30A, the relative sizes of the lightemitters 1044 and light collimators 1302 may be selected such that lightfrom the light emitters 1044 fills the associated light collimators1302. For example, the light emitters 1044 may be spaced sufficientlyfar apart such that micro-lens collimators 1302 having the desiredcurvature may be formed extending over individual ones of the lightemitters 1044. In addition, as noted above, the size and shape of theintra-coupling optical element 1022 b is preferably selected such thatit matches or exceeds the cross-sectional shape and size of the lightbeam 1032 b when incident on that in-coupling optical element 1022 b.Consequently, in some embodiments, a width 1025 of the in-couplingoptical element 1022 b is equal to or greater than the width of themicro-lens 1302 (which may have a width equal to 1045 w or P).Preferably, the width 1025 is greater than the width of the micro-lens1302, or 1045 w or P, to account for some spread in the light beam 1032b. As discussed herein, the width 1025 may also be selected to mitigaterebounce and may be shorter than the length (which is orthogonal to thewidth) of the in-coupling optical element 1022 b. In some embodiments,the width 1025 may extend along the same axis as the direction ofpropagation of incoupled light 1032 b through the waveguide 1020 bbefore being out-coupled for propagation to the eye 210.

With reference now to FIG. 30B, an example of a light projection system1010 with multiple emissive micro-displays 1030 a, 1030 b, 1030 c, andassociated arrays 1300 a, 1300 b, 1300 c of light collimators,respectively, is illustrated. The angular emission profiles of lightemitted by the micro-displays 1030 a, 1030 b, 1030 c are narrowed by thelight collimator arrays 1300 a, 1300 b, 1300 c, thereby facilitating thecollection of a large percentage of the emitted light by the projectionoptics 1070 after the light propagates through the optical combiner1050. The projection optics 1070 then directs the light to an eyepiecesuch as the eyepiece 1020 (e.g., FIGS. 11A and 12-14 ) (not shown).

FIG. 30C illustrates an example of a wearable display system withmultiple emissive micro-displays 1030 a, 1030 b, 1030 c, each with anassociated array 1300 a, 1300 b, 1300 c, respectively, of lightcollimators. The illustrated display system includes a plurality ofmicro-displays 1030 a, 1030 b, 1030 c for emitting light with imageinformation. As illustrated, the micro-displays 1030 a, 1030 b, 1030 cmay be micro-LED panels. In some embodiments, the micro-displays may bemonochrome micro-LED panels, each configured to emit a differentcomponent color. For example, the micro-display 1030 a may be configuredto emit light 1032 a which is red, the micro-display 1030 b may beconfigured to emit light 1032 b which is green, and the micro-display1030 c may be configured to emit light 1032 c which is blue.

Each micro-display 1030 a, 1030 b, 1030 c may have an associated array1300 a, 1300 b, 1300 c, respectively, of light collimators. The lightcollimators narrow the angular emission profile of light 1032 a, 1032 b,1032 c from light emitters of the associated micro-display. In someembodiments, individual light emitters have a dedicated associated lightcollimator (as shown in FIG. 30A).

With continued reference to FIG. 30C, the arrays 1300 a, 1300 b, 1300 cof light collimators are between the associated micro-displays 1030 a,1030 b, 1030 c and the optical combiner 1050, which may be an X-cube. Asillustrated, the optical combiner 1050 has internal reflective surfaces1052, 1054 for reflecting incident light out of an output face of theoptical combiner. In addition to narrowing the angular emission profileof incident light, the arrays 1300 a, 1300 c of light collimators may beconfigured to redirect light from associated micro-displays 1030 a, 1030c such that the light strikes the internal reflective surfaces 1052,1054 of the optical combiner 1050 at angles appropriate to propagatetowards the associated light in-coupling optical elements 1022 a, 1022c, respectively. In some embodiments, in order to redirect light in aparticular direction, the arrays 1300 a, 1300 c of light collimators maycomprise micro-lens or reflective wells, which may be asymmetricaland/or the light emitters may be disposed off-center relative to themicro-lens or reflective wells, as disclosed herein.

With continued reference to FIG. 30C, projection optics 1070 (e.g.,projection lens) is disposed at the output face of the optical combiner1050 to receive image light exiting from that optical combiner. Theprojection optics 1070 may comprise lenses configured to converge orfocus image light onto the eyepiece 1020. As illustrated, the eyepiece1020 may comprise a plurality of waveguides, each of which is configuredto in-couple and out-couple light of a particular color. For example,waveguide 1020 a may be configured to receive red light 1032 a from themicro-display 1030 a, waveguide 1020 b may be configured to receivegreen light 1032 b from the micro-display 1030 b, and waveguide 1020 cmay be configured to receive blue light 1032 c from the micro-display1030 c. Each waveguide 1020 a, 1020 b, 1020 c has an associated lightin-coupling optical elements 1022 a, 1022 b, 1022 c, respectively, forin coupling light therein. In addition, as discussed herein, thewaveguides 1020 a, 1020 b, 1020 c may correspond to the waveguides 670,680, 690, respectively, of FIG. 9B and may each have associatedorthogonal pupil expanders (OPE's) and exit pupil expanders (EPE's),which ultimately out-couple the light 1032 a, 1032 b, 1032 c to a user.

As discussed herein, the wearable display system incorporatingmicro-displays is preferably configured to output light with differentamounts of wavefront divergence, to provide comfortableaccommodation-vergence matching for the user. These different amounts ofwavefront divergence may be achieved using out-coupling optical elementswith different optical powers. As discussed herein, the out-couplingoptical elements may be present on or in waveguides of an eyepiece suchas the eyepiece 1020 (e.g., FIGS. 11A and 12-14 ). In some embodiments,lenses may be utilized to augment the wavefront divergence provided bythe out-couple optical elements or may be used to provide the desiredwavefront divergence in configurations where the out-couple opticalelements are configured to output collimated light.

FIGS. 31A and 31B illustrate examples of eyepieces 1020 having lens forvarying the wavefront divergence of light to a viewer. FIG. 31Aillustrates an eyepiece 1020 having a waveguide structure 1032. In someembodiments, as discussed herein, light of all component colors may bein-coupled into a single waveguide, such that the waveguide structure1032 includes only the single waveguide. This advantageously providesfor a compact eyepiece. In some other embodiments, the waveguidestructure 1032 may be understood to include a plurality of waveguides(e.g., the waveguides 1032 a, 1032 b, 1032 c of FIGS. 11A and 12-13A),each of which may be configured to relay light of a single componentcolor to a user's eye.

In some embodiments, the variable focus lens elements 1530, 1540 may bedisposed on either side of the waveguide structure 1032. The variablefocus lens elements 1530, 1540 may be in the path of image light fromthe waveguide structure 1032 to the eye 210, and also in the path oflight from the ambient environment through the waveguide structure 10032 to the eye 210. The variable focus optical element 1530 may modulatethe wavefront divergence of image light outputted by the waveguidestructure 1032 to the eye 210. It will be appreciated that the variablefocus optical element 1530 may have optical power which may distort theeye 210's view of the world. Consequently, in some embodiments, a secondvariable focus optical element 1540 may be provided on the world side ofthe waveguide structure 1032. The second variable focus optical element1540 may provide optical power opposite to that of the variable focusoptical element 1530 (or opposite to the net optical power of theoptical element 1530 and the waveguide structure 1032, where thewaveguide structure 1032 has optical power), so that the net opticalpower of the variable focus lens elements 1530, 1540 and the waveguidestructure 1032 is substantially zero.

Preferably, the optical power of the variable focus lens elements 1530,1540 may be dynamically altered, for example, by applying an electricalsignal thereto. In some embodiments, the variable focus lens elements1530, 1540 may comprise a transmissive optical element such as a dynamiclens (e.g., a liquid crystal lens, an electro-active lens, aconventional refractive lens with moving elements, amechanical-deformation-based lens, an electrowetting lens, anelastomeric lens, or a plurality of fluids with different refractiveindices). By altering the variable focus lens elements' shape,refractive index, or other characteristics, the wavefront of incidentlight may be changed. In some embodiments, the variable focus lenselements 1530, 1540 may comprise a layer of liquid crystal sandwichedbetween two substrates. The substrates may comprise an opticallytransmissive material such as glass, plastic, acrylic, etc.

In some embodiments, in addition or as alternative to providing variableamounts of wavefront divergence for placing virtual content on differentdepth planes, the variable focus lens elements 1530, 1540 and waveguidestructure 1032 may advantageously provide a net optical power equal tothe user's prescription optical power for corrective lenses. Thus, theeyepiece 1020 may serve as a substitute for lenses used to correct forrefractive errors, including myopia, hyperopia, presbyopia, andastigmatism. Further details regarding the use of variable focus lenselements as substitutes for corrective lenses may be found in U.S.application Ser. No. 15/481,255, filed Apr. 6, 2017, the entiredisclosure of which is incorporated by reference herein.

With reference now to FIG. 31B, in some embodiments, the eyepiece 1020may include static, rather than variable, lens elements. As with FIG.31B, the waveguide structure 1032 may include a single waveguide (e.g.,which may relay light of different colors) or a plurality of waveguides(e.g., each of which may relay light of a single component color).Similarly, the waveguide structure 1034 may include a single waveguide(e.g., which may relay light of different colors) or a plurality ofwaveguides (e.g., each of which may relay light of a single componentcolor). The one or both of the waveguide structures 1032, 1034 may haveoptical power and may output light with particular amounts of wavefrontdivergence, or may simply output collimated light.

With continued reference to FIG. 31B, the eyepiece 1020 may includestatic lens elements 1532, 1534, 1542 in some embodiments. Each of theselens elements are disposed in the path of light from the ambientenvironment through waveguide structures 1032, 1034 into the eye 210. Inaddition, the lens element 1532 is between a waveguide structure 1003 2and the eye 210. The lens element 1532 modifies a wavefront divergenceof light outputted by the waveguide structure 1032 to the eye 210.

The lens element 1534 modifies a wavefront divergence of light outputtedby the waveguide structure 1034 to the eye 210. It will be appreciatedthat the light from the waveguide structure 1034 also passes through thelens element 1532. Thus, the wavefront divergence of light outputted bythe waveguide structure 1034 is modified by both the lens element 1534and the lens element 1532 (and the waveguide structure 1032 in caseswhere the waveguide structure 1003 2 has optical power). In someembodiments, the lens elements 1532, 1534 and the waveguide structure1032 provide a particular net optical power for light outputted from thewaveguide structure 1034.

The illustrated embodiment provides two different levels of wavefrontdivergence, one for light outputted from the waveguide structure 1032and a second for light outputted by a waveguide structure 1034. As aresult, virtual objects may be placed on two different depth planes,corresponding to the different levels of wavefront divergence. In someembodiments, an additional level of wavefront divergence and, thus, anadditional depth plane may be provided by adding an additional waveguidestructure between lens element 1532 and the eye 210, with an additionallens element between the additional waveguide structure and the eye 210.Further levels of wavefront divergence may be similarly added, by addingfurther waveguide structures and lens elements.

With continued reference to FIG. 31B, it will be appreciated that thelens elements 1532, 1534 and the waveguide structures 1032, 1034 providea net optical power that may distort the users view of the world. As aresult, lens element 1542 may be used to counter the optical power anddistortion of ambient light. In some embodiments, the optical power ofthe lens element 1542 is set to negate the aggregate optical powerprovided by the lens elements 1532, 1534 and the waveguide structures1032, 1034. In some other embodiments, the net optical power of the lenselement 1542; the lens elements 1532, 1534; and the waveguide structures1032, 1034 is equal to a user's prescription optical power forcorrective lenses.

Example Light Projection Systems Having Emissive Micro-DisplaysProviding Enhanced Resolution

As described above, a display system (e.g., a wearable display systempresenting AR or VR content) may utilize one or more emissivemicro-displays to reduce the size, mass, and/or power consumptionrelative to systems utilizing various other display technologies. Forexample, the display system may optionally utilize a threshold number ofemissive micro-displays (e.g., three displays each including an array oflight emitters, such as micro-LEDs). In this example, each emissivemicro-display may be configured to generate light of a particularcomponent color. The generated light may be combined to provide theappearance of a full color image, as discussed herein. Various examplesin which multiple emissive micro-displays are utilized are discussedabove, and also discussed below with reference to FIGS. 36A-36B. Asanother example, the display system may optionally utilize a singleemissive micro-display. In this example, the emissive micro-display mayinclude light emitters (e.g., micro-LEDs) of each primary color.

Utilizing the one or more emissive micro-displays, the display systemdescribed herein may be configured to output AR or VR content (“virtualcontent”) at a greater resolution than a resolution directlycorresponding to the number of light emitters included in the emissivemicro-displays. For example, the display system may utilize one or moreactuators to cause movement of or adjustment to one or more parts of alight projection system configured to output light forming virtualcontent to a user. For example, the actuators may adjust geometricpositions associated with the light emitters. As an example, and asillustrated in FIG. 36B, the actuators may cause a change in theposition of the emissive micro-display panels. In this example, themicro-LED panels may be shifted along one or two axes. As anotherexample, and as illustrated in FIG. 36A, the actuator may cause a changein the position of the location of a projection optic (e.g., one or moreprojection lenses). As described herein, the projection optic may routelight generated by one or more micro-LED panels to one or morein-coupling optical elements, such as in-coupling gratings (ICGs). Thein-coupling optical elements may be configured to route the light to auser of the display system.

The adjustment described above may be leveraged to cause geometricpositions of light emitters to assume positions located in inter-emitterregions of the arrays. As described above, an inter-emitter region(e.g., region 1045 illustrated in FIG. 32A) may include a region of anemissive micro-display in which one light emitter is included. Theinter-emitter region may therefore be defined based on one or more pixelpitches. For example, the inter-emitter region may be delineated by afirst side having a length equal to a pixel pitch along a first axis,and second side having a length equal to a pixel pitch along a secondaxis.

FIG. 32A illustrates an example of an emissive micro-display 1030 havingan array 1042 of light emitters (e.g., light emitter 1044) that areseparated by an inter-emitter region 1045. The light emitter 1044 mayhave an emitter size p and a pixel pitch Λ. As illustrated, the lightemitter 1044 may have an emitter size p and a pixel pitch Λ that aresubstantially identical in the x and y directions. However, it should beappreciated that, in some embodiments, the emitter size p and pixelpitch Λ are different in the x and y directions. In addition, differentones of the light emitters of the array 1042 may have different sizes,shapes (e.g., round), compositions, etc. In the illustrated array 1042,a second light emitter on the top row of light emitters is indicated bythe reference 1044′ to facilitate the subsequent discussion herein.

With continued reference to FIG. 32A, in some embodiments the magnitudeof the pixel pitch Λ may be larger than the emitter size p. As discussedherein, emissive micro-display 1030 may have a relatively low fillfactor due to various physical and electrical constraints. For example,each light emitter 1044 may be disposed in an associated area 1049, withonly a minority of that area being occupied by the light emitter 1044.The majority of the area 1049 is occupied by the inter-emitter region1045. The area 1049 may be defined as extending the pixel pitch from anextremity of an associated light emitter 1044 along the x-axis and thepixel pitch from an extremity of the associated light emitter 1044 alongthe y-axis. The low fill factor may undesirably limit the pixel densityand ultimate resolution of images formed using the emissivemicro-display 1030.

In some embodiments, the positions of the light emitters of the array1042, as seen by a user at a first point in time, may be shifted at asecond point in time to locations originally in the inter-emitter region1045, to thereby display pixels corresponding to those locations in animage. Thus, a high-resolution image frame may be broken up into lowerresolution subframes, with a first subframe having pixels at locationscorresponding to a first position of the light emitters, a secondsubframe having pixels at locations corresponding to a second positionof the light emitters, a third subframe having pixels at locationscorresponding to a third position of the light emitters, and so on.Thus, the positions of the light emitters, as seen by the user, may beadjusted in position to effectively tile (e.g., substantially tile) thesubframes of the high-resolution image. It will be appreciated that thesubframes and the high-resolution image frame occupy substantially thesame area (e.g., are substantially the same physical size), as perceivedby a user. For example, the subframes are preferably 90%, 95%, 99%, or100% of the size of the high-resolution image frame, except that theyhave lower pixel density than the high-resolution image frame.

FIG. 32B illustrates an example of how the emissive micro-display 1030of FIG. 32A may be configured to emulate a higher fill-factormicro-display via time-multiplexing and repositioning of the array orassociated optics. As described previously, the emissive micro-display1030 of FIG. 32A may be configured to form, in rapid succession and withoffsets for the perceived positions of individual light emitters,individual partial-resolution subframes. In such embodiments, the visualsystem of a user may merge together the subframes such that the userperceives a full-resolution frame.

With continued reference to FIG. 32B, the illustrated pixels 1044 a-1044c represent the locations of the first light emitter 1044 (FIG. 32A) asseen by a user at different points in time. In addition, the illustratedpixels 1044 a′-1044 c′ represent the locations of the second lightemitter 1044′ (FIG. 32A) at the same points in time as the illustratedpixels 1044 a-1044 c, respectively. The first light emitter 1044 at afirst position may emit light for pixel 1044 a of a first subframe. Thispixel may represent a first pixel 1044 a of a rendered frame of virtualcontent. The perceived position of the first light emitter 1044 may thenbe shifted by a distance less than the pixel pitch Λ along the axis ofthe shift (e.g., by Δx and/or Δy) and the first light emitter 1044 mayemit light for a pixel 1044 b in a second subframe. As illustrated, theposition of the first light emitter 1044 has shifted by Δx along thex-axis. The pixel 1044 b may thus be a second pixel 1044 b of therendered frame of virtual content. As will be described below, thegeometric position of the first light emitter 1044 may be shifted via anactuator connected to the array 1042 (FIG. 32A). Thus, the first lightemitter 1044 may be physically relocated in three-dimensional space. Thegeometric position may also be shifted via an actuator connected to aprojection optic through which light from the first light emitter 1044is routed. Thus, the first light emitter 1044 may remain in a samephysical location, and its light may be shifted by shifting the positionof the projection optics relative to the first light emitter 1044.

With continued reference to FIG. 32B, subsequent to shifting thegeometric position of the first light emitter 1044 for the pixel 1044 b,the first light emitter 1044 may again be shifted (by 4 x asillustrated) and the first light emitter 1044 may emit light for a pixel1044 c in a third subframe of the rendered frame of virtual content.This pixel 1044 c may represent a third pixel of the rendered frame.This process may be repeated for a total N subframes, which togetherform the full resolution rendered frame of virtual content. Theremaining light emitters of the array 1042 may similarly emit light,over multiple offset subframes, for multiple pixels in the full frame.In the example of FIG. 32B, this process is repeated for 9 subframes,such that the first emitter 1044 provides all 9 pixels fitting withinthe area 1049. In this way, the array 1042 (FIG. 32A) may be outputvirtual content with a resolution which is three times greater in the xdirection, and three times greater in the y direction, as compared tothe resolution of the array 1042.

In some embodiments, the perceived positions of the array 1042 of lightemitters may be updated in a substantial continuous movement. Forexample, the position of emitter 1044 may be shifted continuously alongan x direction until output of pixel 1044 c. The display system (e.g.,one or more processors or processing elements) described herein maydetermine an extent to which the position of emitter 1044 has beenshifted during this continual movement. The display system may beconfigured to determine a time at which to output light corresponding toa new pixel. For example, the display system may identify that aposition of emitter 1044 has reached a distance corresponding to pixel1044 b. The display system may then cause the emitter 1044 to outputlight based on an image value associated with pixel 1044 b in the secondsubframe. Utilizing such continual adjustment of the geometric positionsmay reduce jerkiness associated with shifting the geometric positions.In some other embodiments, the geometric positions may be shifted indiscrete steps. For example, emitter 1044 may output light correspondingto pixel 1044 a. The geometric position of emitter 1044 may then beshifted in a discrete step and paused to output light corresponding topixel 1044 b. Other light emitters of the array 1042 may similarly beshifted along with the light emitter 1044. For example, the lightemitter 1044′ may be shifted in discrete steps to provide the pixels1044 a′, 1044 b′, and 1044 c′ at different ones of the discrete steps.

In some embodiments, the number of subframes N may be determined orlimited by the physical properties of the array 1042. An exampleproperty may include a maximum framerate (e.g., N is preferably not beso large that subframes fail to merge together in users' visual systems;that all N subframes are preferably displayed over a time duration thatis less than the flicker fusion threshold of the user, e.g., less than1/60 of a second). Additional example properties may include the emitterpitch Λ, the emitter size p, and so on. As described above, the numberof subframes N may be determined based on a number of positions in whichan emitter of the array 1042 may fit within an inter-emitter region1045. In the example of FIG. 32B, the first emitter 1044 may be placedin 9 distinct positions within the inter-emitter region 1045. Thus,there may be up to 9 subframes. If the emitter size p were larger and/orif the emitter pitch Λ were smaller, then the number of subframes N maybe reduced. Similarly, if the emitter size p were smaller and/or if theemitter pitch Λ were larger, then the number of subframes N may beincreased.

In some embodiments, N may be determined based on computing a floor ofthe emitter pitch Λ divided by the emitter size p. The computed floormay represent a number of times an emitter may be adjusted or moved ineach direction. For example, if Λ=2.5 micron and p=0.8 micron, then Nwould equal 3. Thus, there may be 9 subframes (e.g., 3×3). It will beappreciated that this determination may be adjusted depending on whetheremitter pitch Λ and/or emitter size p varies along the x and ydirections. For example, there may be emitter pitch_(X) Λ_(X) andemitter pitchy Λ_(Y). In this example, N may thus vary based ondirection. The number of subframes may be determined as beingN_(X)×N_(Y).

Example Emissive Micro-Display for Forming Foveated Images

Another potentially desirable feature in VR, AR, and MR applications isfoveated imaging (also referred to simply as foveation), in which theresolution of a displayed image varies across that image. In particular,VR, AR, and MR may include eye tracking systems that determine whereusers are looking. Given the limitations of the human visual system,which generally detects fewer details in portions of the field of viewaway from a user's fixation point, presenting full resolution content(e.g., content at the full-rendered resolution) at the periphery ofusers' vision may be undesirable. The peripheral full resolution contentmay consume excessive processing power in rendering and have excessivepower consumption when displayed by the display system. In other words,significant benefits may be achieved in terms of reduced processingloads and display power consumption by reducing the resolution ofcontent away from a user's fixation point and by delivering the highestresolution image content only to the part of the viewing field that theuser is looking, for example, at and immediately adjacent the fixationpoint. It will be appreciated that the fixation point corresponds to theportion of the field of view that is focused onto the fovea of theuser's eye; thus, the eye has relatively high sensitive to detail inthis portion of the field of view.

Foveation may also be based on factors other than fixation point. As anexample, content creators may specify that certain content, such astext, be displayed at full resolution even if the user is looking awayfrom the content. As another example, content creators may specify thatfoveation should only be active under certain conditions. As yet otherexamples, foveation may be a user selectable setting or may beautomatically enabled as a result of a low battery condition. In atleast some embodiments, foveation may conserve display resources (data,pixels, bandwidth, computation) by delivering the highest resolutiononly to portions of an image in the part of the field of view that theuser is fixating on (e.g., represented by foveal region A in FIG. 33 ),while delivering a lower resolution image to the peripheral part (e.g.,represented by peripheral region B in FIG. 33 ).

FIGS. 32C, 32D, and 33 illustrate examples of configurations of thearray 1042 of FIG. 32A for providing foveated images 1130, 1140, and1200, respectively.

FIG. 32C illustrates an example of a foveated image 1130 formed by anemissive micro-display, such as the emissive micro-display 1030 of FIG.32A. The array 1042 of FIG. 32A may be configured to provide two levelsof resolution for the rendered image 1130 of virtual content. Inparticular, the light emitter array 1042 may provide full-resolution (orrelatively high resolution) in a foveal region 1132 (the portion of theimage expected to be focused onto the user's fovea) and may provide apartial-resolution (relatively low resolution) in a second region 1134.The location of the foveal region 1132 may be determined according tothe location of a user's fixation point. For example, a gaze detectionscheme may be employed. The gaze detection scheme may track eyes of theuser. As an example, a pupil may be identified in each eye. A vector maybe extended from each identified pupil and an intersection of thevectors in three-dimensional space may be determined. This intersectionmay represent a fixation point of the user. The foveal region 1132 maycorrespond to a portion of the rendered image 1130 which is within athreshold angular distance of this fixation point. Additional detailsregarding foveation and the detection of a user's fixation point may befound in U.S. Patent App. Pub. No. 2018/0275410, the entire disclosureof which is incorporated by reference herein.

To provide a high resolution for the foveal region 1132, whilemaintaining a lower resolution for the second region 1134, the lightemitters 1044 of the array 1042 (FIG. 32A) may be updated differently.With reference again to the example of FIG. 32B, in which an emitter wasupdated N (e.g., 9) times for a full-resolution frame of virtualcontent, a portion of the light emitters 1044 that correspond to pixelsin the foveal region 1132 may be updated N times. In contrast, aremaining portion of the light emitters 1044 which correspond to pixelsin the second region 1134 may be updated less than N times (e.g., once,2 times, 3, times, and so on) per rendered frame. As an example, theperceived positions of the light emitters 1044 may be shifted asdescribed herein. For light emitters corresponding to the foveal region1132, the light emitters 1044 may be updated for each shift in perceivedlight emitter position. For example, these emitters may generate lightcorresponding to an updated pixel value included for each emitterposition. The updated pixel values may represent pixel values includedin respective subframes of the full-resolution frame of virtual content.For emitters included in the second region 1134, the emitters may not beupdated for every shift. For example, these emitters may generate lightcorresponding to a same pixel value for two or more geometric positions,or may simply not output light. As a result, these emitters may skip(e.g., not present) pixel values included in one or more of thesubframes.

The second region 1134 is illustrated in FIG. 32C as having theresolution of the physical array of emitters included in array 1042,however this is merely one option. If desired, the partial-resolution inthe second region 1134 may have a resolution lower than the resolutionof the physical array 1042. For example, a portion of the emitters inregion 1134 may be deactivated. Alternatively, the second-region mayhave a resolution higher than the resolution of the physical array 1042.For example, the perceived positions of the light emitters correspondingto region 1134 may be shifted to display pixels for multiple subframesper image frame 1130, although the number of pixels displayed in region1134 per rendered frame is less than in the foveal region 1132.

FIG. 32D illustrates an example of an emissive micro-display, such asthe emissive micro-display 1030 of FIG. 32A, configured to form foveatedimages with three or more levels of resolution within the image. For theillustrated displayed image 1140, the array 1042 of FIG. 32A may beconfigured to provide three levels of resolution in each display image1140, with first region 1142 having full resolution, the second region1144 having an intermediate resolution, and the third region 1146 havinga low resolution. In general, the array 1042 may be configured toimplement foveation with any desired number of regions of differentresolution and the resolution at any location within the display may bearbitrarily selected (e.g., by selecting how many of the pixels of thetotal subframes are utilized for each light emitter location of thearray). For example, for pixels in the first region 1142, thecorresponding light emitters may present the pixel information for everysubframe, for the second region 1144 the corresponding light emittersmay present the pixel information for fewer subframes, and for the thirdregion 1146 the corresponding light emitters may present the pixelinformation for yet fewer subframes. In some embodiments, it may bedesirable to transition smoothly between high-resolution andlow-resolution regions. Such transitioning can be accomplished bygradually reducing the number of subframes that individual lightemitters present information for, as discussed above.

With reference to FIGS. 32C and 32D, the foveal regions (e.g., regions1132 and 1142) and the transition region 1144 are shown as rectangles(squares) for ease of illustration, and it will be appreciated thatthese regions may assume any shape. For example, these regions may haveshapes that are circular, star-shaped, oval, etc. FIG. 33 illustratesanother example of a foveated image provided by an emissivemicro-display. As shown in FIG. 33 , the highest resolution may beprovided only to the foveal part 1202, which may have a circular shapeand is represented by region A 1202. Outside the foveal portion of thefield of view (e.g., in region B 1204), the resolution of the displayedimage may be reduced, thereby reducing processing loads associated withrendering and reducing display power consumption.

In each of FIGS. 32C, 32D, and 33 , the location of the high-resolutionportion of the foveated image may be determined according to the user'seye pose or gaze direction (e.g., as determined by an eye-trackingsystem including components such as camera assembly 630, FIG. 6 ). Asexamples, the high-resolution portion (e.g., foveal region 1132, firstregion 1142, and region A 1202) may be roughly in the center of thefoveated image when the user is looking straight ahead, and thehigh-resolution portion may be off to the left side when the user islooking left. In this manner, the user may be presented with relativelyhigh resolution images along the direction of the user's gaze (e.g., atthe fixation point), while the user is presented with lower resolutionin portions of images in their peripheral vision.

Example Movements of Emissive Micro-Display and/or Display Optics

As discussed herein, the positions of displayed pixels may be shifted byshifting the physical positions of parts a light projection system, suchas, for example, light emitters 1044 (FIG. 32A) and/or projection optics1070 (FIGS. 11A, 12-14, 24A-24B, 26A-26C, and 29-30C). As also discussedherein, the physical positions may be shifted using an actuatormechanically connected to the part to be shifted. It will be appreciatedthat the positions of light emitters may be shifted by, for example,shifting an array containing the light emitter.

In some embodiments, these shifts may be made in discrete steps. Forexample, the light emitters and/or projection optics may be stationaryor substantially stationary while they emit light to form pixels of anindividual subframe. The positions of the light emitters and/orprojection optics may then be shifted between the presentation ofdifferent subframes.

In some embodiments, the light emitters and/or projection optics may becontinuously moved between subframes with or without a reduction invelocity while the light emitters are displaying or projecting anindividual subframe. Such continuous movement may advantageously besimpler to implement than precisely starting and stopping the movementof the light emitters and/or projection optics in small steps. In eithercase, the result remains that the relatively low-resolution andlow-fill-factor array 1042 (FIG. 32A) emulates a relativelyhigh-resolution and high-fill factor array.

FIG. 34 illustrates various example paths of movement of parts of anemissive micro-display to shift the positions of displayed pixels. Forexample, as described herein, the movements may be made using actuatorsconnected to one or more emissive micro-displays or connected to one ormore projection optics. The actuators may cause the emissivemicro-displays and/or projection optics to move on a plane along theillustrated paths. In FIG. 34 , each numbered position may be understoodto be a position at which light for a pixel of a different subframe isemitted; thus, each numbered position is associated with a differentsubpixel. Preferably, one loop of the various paths of movement arecompleted and returned to the initial position within the flicker fusionthreshold.

In some embodiments, the movements may be made through use of twoactuators. For example, a first actuator may adjust movement in a firstdirection (e.g., an x-direction) and a second actuator may adjustmovement in a second direction (e.g., a y-direction). In someembodiments, the first actuator and second actuator may operate inquadratures (e.g., 180 degrees phase shift relative to each other). Asan example, the first actuator may perform a cosine motion while thesecond actuator may perform a sine motion, with the two motionscombining to define a circle. Consequently, in some embodiments, it willbe appreciated that the various actuators (e.g. actuators 1504, 1504a-c, etc.) herein may be understood to be an aggregate structureencompassing two constituent actuators, each providing movement along aparticular axis.

With continued reference to FIG. 34 , in movement pattern 1300, thegeometric positions may move (e.g., oscillate) back and forth betweentwo points, thus providing a perceived pixel resolution that is doublethe base resolution of the array. It will be appreciated the baseresolution is the resolution provided by the array without shifting thearray as discussed herein. In movement pattern 1302, the path ofmovement may define a triangular shape, which may increase the baseresolution of the array 1042 by up to a factor of three. In movementpattern 1304, the path of movement may define a rectangular pattern,thus increasing the base resolution of the array 1042 by up to a factorof four. In movement pattern 1306, the geometric positions may move in arectangular pattern, thus increasing the base resolution of the array1042 by up to a factor of six. It will be appreciated that a differentsubframe is not necessarily presented at each numbered position and, asa result, as described above, the increase in resolution may be “up to”a certain factor.

In some embodiments, with continued reference to FIG. 34 , it will beappreciated that other additional subframes may be presented on each legof the various illustrated paths. For example, on the leg from position1 to position 2 of movement path 1300, one or more subframes may bepresented at different points on that path between positions 1 and 2. Insuch an arrangement, the increase in resolution may be at least theassociated factors noted above for each of the movement patterns.

With reference now to FIGS. 35A and 35B, examples are illustrated of howdisplacement of light emitters and projection optics may change theposition of a displayed pixel. As shown in FIG. 35A, displacing anobject point (e.g., an individual light emitter) by δ along a line on aplane 1400, which may be representative of displacing an array alongthat line, changes the direction of the light ray transmitted throughprojection optic 1070 from a first direction α₁ 1404 to a seconddirection α₂ 1406. This change in direction, then, will cause the pixelprovided by the illustrated light emitter to shift, since the positionof the light emitter has shifted. The direction of the light raytransmitted through the projection optics 1070 may have a roughly 1-1correspondence with position of an object point. Thus, an emissivemicro-display may be shifted along one or more axes to shift thelocation of a displayed pixel.

As shown in FIG. 35B, displacing a projection optics 1070 by δ alsochanges the direction of the transmitted light ray from the firstposition α₁ 1404 to the second position α₂ 1406. It should beappreciated that a shifting of the projection optics 1070 along one ormore axes may be based on physical characteristics associated with theprojection optic 1070. For example, an extent to which the projectionoptics 1070 is adjusted upwards may depend on physical characteristicsof the projection optics 1070, and the impact of the projection optics1070 on the path of light. Example characteristics may include focallength, a type of the lens, refractive index, radius of curvature, andso on.

Thus, the techniques described herein for enhancing the resolution of anemissive micro-display may be accomplished via displacements of theprojection optics or other optical component between the emissivemicro-display and the user. Moreover, and as described above withrespect to FIGS. 9A-9E, a full-color emissive micro-display may employthree emissive micro-displays each having a different color (e.g., a redarray, a green array, and a blue array) whose light is opticallycombined and then projected through common projection optics. In suchembodiments, it may be simpler to implement controlled displacements ofthe common optics, as it may require only a single displacement actuator(or set of actuators) to displace the common optics as described herein,instead of a displacement actuator (or set of actuators) for each of theemissive micro-displays.

Example Emissive Micro-Display Systems

As discussed herein, the various parts of a light projection system maybe moved to provide the desired shifting of positions of displayedpixel, and this movement may be achieved using actuators mechanicallyconnected to the parts to be moved.

FIG. 36A illustrates an example of a wearable display system having alight projection system with an actuator coupled to projection optics.The light projection system 1010 and the actuator 1504 may be referredto together as the projection system 1500. It will be appreciated thatthe light projection system 1010 of the projection system 1500 mayassume any of the various configurations disclosed herein (e.g., asillustrated and discussed regarding FIGS. 11A, 12-14, 24A). To theextent that micro-lenses, micro-reflectors, or gratings are utilizedwith the light emitters of the projection system 1500 (e.g., asillustrated in FIGS. 24B, 26A-26C, and 29-30C), the micro-lenses,micro-reflectors, or gratings are preferably configured to provide aneffective pixel size less than the pixel pitch to allow a sufficientlysparse array to facilitate the position shifting described herein.Additionally, as discussed herein, the actuator 1504, or actuators 1504a-1504 c, may each include, or otherwise represent, two actuators whichcause movement along different axes.

With continued reference to FIG. 36A, an example of an actuator is apiezoelectric actuator. The actuator 1504 may adjust the position of theprojection optics 1070 along one or more axes on a plane (e.g. a planeparallel to the plane on which the eyepiece 1020 is disposed) asdescribed herein. For example, the actuator 1504 may move the projectionoptics 1070 along two crossing axes on that plane (e.g., using atwo-dimensional piezoelectric motor). As illustrated, the projectionoptics outputs light from the emissive micro-displays 1030 a-1030 c tothe in-coupling optical elements 1022 a-1022 c of the waveguides of theeyepiece 1020.

The light projection system 1010 may utilize monochrome emissivemicro-displays 1030 a, 1030 b, 1030 c, each configured to output adifferent component color. An optical combiner 1050, such as a dichroicx-cube, may redirect the light emitted from the emissive micro-displays1030 a-1030 c to the projection optics 1070 as described above.

In some embodiments, the projection optics 1070 is configured to receiveimage light from the emissive micro-displays 1030 a-1030 c, the actuator1504 is configured to move the projection optics 1070, which then causesthe image light outputted by the light projection system 1500 to shift.Thus, the pixels presented by an array may be perceived to be adjustedin location, for example to tile subframes across an inter-emitterregion as described herein; the emissive micro-displays 1030 a-1030 cmay output light corresponding to a plurality of subframes. Thesesubframes may be presented in rapid succession (within the flickerfusion threshold), such that a user may perceive them as being presentsimultaneously in a full resolution frame of virtual content.

In some embodiments, one or more of the emissive micro-displays 1030a-1030 c are independently moveable relative to others of the emissivemicro-displays, the optical combiner 1050, and the projection optics1070. In such embodiments, each independently moveable micro-display mayhave an associated independently moveable actuator 1504. FIG. 36Billustrates an example of a wearable display system having a lightprojection system 1500 with multiple actuators 1504 a-1504 c, eachcoupled to a different emissive micro-display 1030 a-1030 c. Theactuators 1504 a-1504 c may thus shift its associated component coloremissive micro-displays 1030 a-1030 c. This embodiment may allow eachcomponent color emissive micro-display 1030 a-1030 c to be shifted to arespective position to output a same subframe such that the subframeoverlaps in the eyes of the user. In some embodiments, the componentcolor emissive micro-displays 1030 a-1030 c may be shifted alongdifferent paths.

With reference again to FIGS. 36A-36B, the actuators 1504 or 1504 a-1504c may be controlled via one or more processing elements included in thedisplay system. Additionally, the output of image light by the emissivemicro-displays 1030 a-1030 c may be synchronized with movement of theactuators 1504 or 1504 a-1504 c. For example, the emissivemicro-displays 1030 a-1030 c may output light based on a signal, orinstruction, indicating that the actuators 1504 or 1504 a-1504 c, theparts of the light rejection system 1500 moved by the actuators, havebeen shifted to one or more positions. This signal, or instruction, maybe utilized for a continual movement pattern or a discrete movementpattern as described above. The signal or instruction may be generatedby a display system, such as one or more processors or processingelements. In some embodiments, the light projection system 1500 is partof the display system 60 (FIG. 9E) and the control elements for theactuator 1504 and the emissive micro-displays 1030 a-1030 c may be partof the processing modules 140 or 150 (FIG. 9E).

In some embodiments, actuators 1504 or 1504 a-1504 c may continuallymove the mechanically coupled part of the light projection system 1500,for example according to the movement patterns illustrated in FIG. 34 ,and the emissive micro-displays 1030 a-1030 c may periodically generatelight. With respect to a continual movement pattern, the emissivemicro-displays 1030 a-1030 c may be synchronized with a signal (e.g., aclock signal) utilized also by the actuators 1504 and/or 1504 a-1504 c,to thereby present subframes at the desired location of those subframes.For example, the actuator 1504 may shift the projection optics 1070according to a known movement pattern (e.g., known velocity based on theclick signal). Thus, the emissive micro-displays 1030 a-1030 c mayutilize the signal to identify an extent to which the projection optics1070 has been moved along the movement pattern. The emissivemicro-displays 1030 a-1030 c may then output light, for example,corresponding to a new subframe, when the projection optics 1070 is in aposition associated with the new subframe.

In some embodiments, as discussed herein, time division multiplexing maybe utilized for the micro-displays 1030 a, 1030 b, 1030 c. For example,different ones of the emissive micro-displays 1030 a, 1030 b, 1030 c,may be activated at different times to generate different componentcolor images.

In some embodiments, the actuators 1504 a-1504 c may be moved tocomplete at least one movement loop (e.g., a loop of the movements paths1300-1306, FIG. 34 ) with only a single one of the emissivemicro-displays 1030 a-1030 c generating subframes of a single componentcolor during that loop. In some embodiments, after completing one loop,subframes of a second component color are generated by a second one ofthe micro-displays during a second loop of actuator movement; and aftercompleting that second loop, subframes of a third component color aregenerated by a third one of the micro-displays during a third loop ofactuator movement. Thus, each of the loops of actuator movement generatea set of tiled subframes, for a total of three sets of loops andsubframes where there are three component colors (the number of setsbeing equal to the number of component colors). Preferably, completesets of subframes of each component are completed within a flickerfusion threshold.

While the eyepiece 1020 is illustrated in FIGS. 36A-36B as including astack of waveguides, it will be appreciated that the eyepiece 1020 mayinclude a single waveguide in some embodiments, as disclosed herein.FIG. 37A illustrates an example of a wearable display system having alight projection system 1500 with an eyepiece 1020 having a singlewaveguide 1020 a. The illustrated single waveguide eyepiece 1020 may besimilar to that illustrated in and discussed regarding FIGS. 13B, 14,30A, and 31A-31B.

Additionally, as discussed herein, a single micro-display may emit lightof two or more (e.g., all) component colors (e.g., emit red, green, andblue light). For example, FIG. 14 illustrates an example of a wearabledisplay system with a single full-color emissive micro-display 1030 bwhich may emit light of each component color. In some embodiments, sucha micro-display and/or the related projection optics may be shifted topresent different pixels of an image, as discussed herein.

FIG. 37B illustrates an example of a wearable display system having alight projection system 1010 in which a single array of light emittersoutputs light of one or more different component colors. As illustrated,the light projection system 1010 may include an emissive micro-display1030 b including an array 3742 of light emitters 3744. In someembodiments, the array 3742 may be configured to emit light of allcomponent colors utilized by the display system to form a full-colorimage. For example, the micro-display 1030 b may include an array oflight emitters which each generate red, green, and blue light.

Preferably, each component color for a given pixel is emitted from anoverlapping area of the array 3742, which may advantageously facilitatethe shifting described herein for providing different pixels of animage. For example, the light emitters 3744 may be understood to eachinclude a stack of constituent light generators, with each constituentlight generators being configured to emit light of a differentassociated component color. The micro-display 1030 b may, in someembodiments, include coaxial red, green, and blue stacked constituentlight generators.

Advantageously, with continued reference to FIG. 37B, by emitting eachcomponent color, the micro-display 1030 b may thus avoid use of anoptical combiner, such as the optical combiner 1050 described herein.The light (e.g., multi-component light) from the micro-display 1030 bmay be routed through projection optics 1070 to the eyepiece 1020. Asdescribed above, with respect to at least FIG. 36A, an actuator 1504 mayadjust the position of the projection optics to form different pixels ofan image. In some embodiments, a single waveguide eyepiece 1020 may beused to receive light (e.g., via an in-coupling optical element 1122 aconfigured to in couple incident light of each of the component colors).

While FIG. 37B illustrates the actuator 1504 adjusting the position ofthe projection optics 1070, it may be understood that the actuator 1504may in addition or alternatively be attached to the micro-display 1030 bto adjust the position of the micro-display 1030 b, to shift themicro-display 1030 b to provide different pixels as discussed herein.FIG. 37C illustrates a wearable display system similar to that of FIG.37B, except that the actuator 1504 is attached to the micro-display 1030b instead of the projection optics 1070.

As described above, in some embodiments where different micro-displaysare utilized to generate light of different component colors, theprojection system may use an optical combiner to combine the separatelygenerated light of different colors. For example, an x-cube may beemployed to combine light from different micro-displays 1030 a-1030 c(FIG. 36B). The combined light may be routed through projection optics1070 and directed to an eyepiece 1020 including one or more waveguides.

In some embodiments, and as illustrated in FIGS. 38A-38D, even wheredifferent micro-displays are utilized to generate light of differentcomponent colors, an optical combiner may be omitted from the projectionsystem 1500. For example, the micro-displays 1030 a-1030 c may eachroute light via a dedicated associated one of the projection optics 1070a-1070 c to the eyepiece 1020. As illustrated, micro-display 1030 a hasan associated projection optics 1070 a which focuses light ontoassociated in-coupling optical elements 1022 a, micro-display 1030 b hasan associated projection optics 1070 b which focuses light ontoassociated in-coupling optical elements 1022 b, and micro-display 1030 chas an associated projection optics 1070 c which focuses light ontoassociated in-coupling optical elements 1022 c.

It will be appreciated that in embodiments in which an optical combiner1500 is not used, several example benefits may be achieved. As anexample, there may be improved light collection as the micro-displays1030 a-1030 c can be placed closer to the projection optics 1070 a-1070c when the intervening optical combiner 1500 is omitted. As a result,higher light utilization efficiency and image brightness may beachieved. As another example, the projection system 1500 may besimplified and tailored to light of a particular component color. Forexample, an optics design for each respective projection optics 1070a-1070C may be calibrated separately for light of each component colorgenerated by the micro-displays 1030 a-1030 c. In this way, theprojection system 1500 may avoid the need for achromatization of theprojection optics.

As another example benefit, and as illustrated in FIG. 38A, light fromeach of the projection optics 1070 a-1070 c may advantageously be morespecifically focused onto respective associated in-coupling opticalelements 1022 a-1022 c. With respect to FIGS. 36A-36B, the combinedlight is routed via the projection optics 1070 onto the eyepiece 1020.As illustrated, the light may be in-coupled via different in-couplingoptical elements 1022 a-1022 c. In the examples of FIGS. 36A-36B, theeyepiece 1020 includes three example waveguides which in-couplerespective component colors generated by the micro-displays 1030 a-1030c. However, it will be appreciated that each component color may notprecisely focus on a respective in-coupling element 1022 a-1022 c of theeyepiece 1020. As a non-limiting example, FIGS. 36A-36B illustrate thecombined light focusing at a depth between in-coupling elements 1022 band 1022 c.

In contrast, the examples of FIG. 38A-38B allow for more precisefocusing of each component color onto a respective in-coupling element1022 a-1022 c. The projection optics 1070 a-1070 c for each componentcolor may be configured to precisely focus light onto a respectivein-coupling element 1022 a-1022 c. In some embodiments, this precisefocusing may improve image quality by providing well-focused images ofeach component color.

FIG. 38A illustrates an example of a light projection system 1500without an optical combiner (e.g., the optical combiner 1050 describedabove). In the illustrated example, three micro-displays 1030 a-1030 cprovide light (e.g., component color light) to respective projectionoptics 1070 a-1070 c. The projection optics 1070 a-1070 c may beconnected to, or otherwise positioned along, a connecting element 3802.The connecting element 3802 may be adjusted in position by an actuator1504. Thus, the actuator 1504 may adjust positions of the projectionoptics 1070 a-1070 c, which form a unitary structure. Light from eachmicro-display 1030 a-1030 c may be routed through the projection optics1070 a-1070 c and focused onto respective in-coupling elements 1022a-1022 c included in the eyepiece 1020.

FIG. 38A illustrates the actuator 1504 adjusting the positions of theprojection optics 1070 a-1070 c via the connecting element 3802. In someembodiments, each projection optics 1070 a-1070 c may include its owndedicated actuator. For example, the projection system 1500 may includethree actuators for adjusting positions of a respective one of the threeprojection optics 1070 a-1070 c.

FIG. 38B illustrates another example of a wearable display system havinga light projection system without an optical combiner. In someembodiments, the micro-displays 1030 a-1030 c may form a single integralunit, e.g., the micro-displays 1030 a-1030 c be placed on a singleback-plane 3804. In some embodiments, the back-plane 3804 may be asilicon back-plane, which may include electrical components for themicro-displays 1030 a-1030 c. Similar to FIG. 38A, the illustratedactuator 1504 may adjust position of the connecting element 3802.

It will be appreciated that the actuators of FIGS. 38A-B may be attachedto and configured to move the micro-displays 1030 a-1030 c rather thanthe projection optics 1070 a-1070 c. For example, FIG. 38C illustrates awearable display system which is otherwise similar to the wearabledisplay system of FIG. 38A, except that the actuator 1504 attached tothe projection optics 1070 a-1070 c is omitted, and each of themicro-displays 1030 a-1030 c instead has an associated actuator 1504a-1504 c, respectively. In some embodiments where the micro-displays1030 a-1030 c are joined together (e.g., where two or more of themicro-displays or physically connected, e.g., by sharing a commonback-plane), a single actuator 1504 may be utilized to change theposition of the physically connected ones of the micro-displays 1030a-1030 c. For example, FIG. 38D illustrates a wearable display systemwhich is otherwise similar to the wearable display system of FIG. 38B,except that the actuator 1504 attached to the projection optics 1070a-1070 c is omitted, and the actuator 1504 is instead attached to thephysically conjoined micro-displays 1030 a-1030 c so as to move thesemicro-displays together.

In the description above, with respect to at least FIGS. 36A-38D, one ormore actuators are described as causing displacement or movement ofdifferent components of the wearable display system. While in each ofthese figures one or more actuators are illustrated for ease ofillustration and discussion as moving the same type of component (e.g.,micro-display or projection optics), in some embodiments, actuators maybe provided for adjusting the positions of two or more types ofcomponents (e.g., in the same display system, actuators may be attachedto and configured to adjust the positions of both the micro-displays andthe projection optics illustrated in these Figures).

For example, FIG. 36A illustrates an actuator 1504 for adjusting theposition of projection optics 1070, and FIG. 36B illustrates actuators1504 a-1504 c for adjusting the positions of micro-displays 1030 a-1030c, respectively. In some embodiments, the wearable display system mayinclude both the actuator 1504 and actuators 1504 a-1504 c, withactuator 1504 configured to adjust the position of the projection optics1070 while actuators 1504 a-1504 c are configured to adjust thepositions of micro-displays 1030 a-1030 c. For example, the positions ofthe projection optics 1070 may be adjusted at the same time as thepositions of the micro-displays 1030 a-1030 c. As another example, thepositions of projection optics 1070 and micro-displays 1030 a-1030 c maybe adjusted at different times (e.g., sequentially).

Similarly, with reference to FIGS. 37B and 37C, in some embodiments,both micro-display 1030 b and projection optics 1070 may have anassociated actuator 1504 for moving the micro-display 1030 b andprojection optics 1070, respectively (e.g., for moving these componentsat the same time or at different times). In some embodiments, the samedisplay system may include and use both actuator 1504 (illustrated inFIG. 38A) and actuators 1504 a-1504 c (illustrated in FIG. 38C) foradjusting the positions of projection optics 1070 a-1070 c andmicro-displays 1030 a-1030 c, respectively. With reference to FIGS. 38Band 38D, in some embodiments, the same display system may include theprojection optics 1070 a-1070 c with a first associated actuator 1504and the conjoined micro-displays 1030 a-1030 c may each have a secondassociated actuator 1504.

Example Flowchart

FIG. 39 illustrates a flowchart of an example process for outputtingsubframes of a rendered frame of virtual content. For convenience, theprocess will be described as being performed by a display system havingone or more processors (e.g., in the local processing and data module140 or in the remote processing module 150 of FIG. 9E).

At block 3902, the display system obtains a rendered frame of virtualcontent. As described above, the display system may generate frames ofvirtual content for presentation to a user. For example, the localprocessor and data module 140 may include one or more graphicsprocessing elements. The module 140 may then generate rendered frames ofvirtual content.

As described in FIGS. 32-36 , the rendered frame may be rendered, atleast in part, at a resolution (e.g., pixel density) greater than thatof the light emitters (e.g., micro-LEDs) included in the micro-displaysof a light projection system. Each subframe may be formed based on lightgenerated by the light emitters. Each set of subframes for forming afull resolution frame may be successively output in rapid succession(e.g., within the flicker fusion threshold), such that they may beperceived by the user as being simultaneously present to form the fullresolution rendered frame.

At block 3904, the display system outputs light forming a firstsubframe. The display system may select pixels included in the renderedframe as forming the first subframe. For example, and as described inFIGS. 32A-32D, there may be a threshold number of subframes (e.g., 9subframes). Thus, the display system may select the pixels correspondingto a first of these threshold number of subframes. For example, thedisplay system may divide the rendered frames into the threshold numberof subframes. The display system may then store these subframes andcause the emissive elements to generate light forming each subframe.Optionally, the module 140 may be configured to generate subframesinstead of the full rendered frame. The display system then causes thelight projection system to output light forming the first subframe. Itwill be appreciated that the pixels of the various subframes areinterleaved or intermixed, such that pixels of different subframes mayoccupy the spaces separating pixels of other subframes.

At block 3906, the display system shifts the positions of displayedpixels. As described in FIGS. 35A-35B, the pixel positions may beperceived to be adjusted in position via actuators that move parts ofthe light projection system, to change the path of light through thatlight projection system. For example, the one or more actuators mayadjust the positions of one or more emissive micro-displays included inthe light projection system. As another example, the one or moreactuators may adjust the positions of projection optics included in thelight projection system. These adjustments may cause light from theemissive elements to be adjusted in position.

As described above, the display system may continually move parts of thelight projection system. For example, the actuators may follow amovement pattern such as the movement patterns illustrated in FIG. 34 .The display system may also cause discrete adjustments of the lightprojection system via the one or more actuators. For example, thepositions of the various parts of the light projection system may bediscretely adjusted for each subframe.

At block 3908, the display system outputs light forming a secondsubframe after changing the position of moveable parts of the lightprojection system, so that the light forming the second subframeprovides pixels at a desired location for the second subframe. Thedisplay system may select pixels of the rendered frame forming thesecond subframe. Optionally, the module 140 may render the secondsubframe. The display system may then cause the light projection systemto output light forming the second subframe.

The display system may then continue to shift the positions of displayedand output successive subframes until the full rendered frame is formed.

Various example embodiments of the invention are described herein.Reference is made to these examples in a non-limiting sense. They areprovided to illustrate more broadly applicable aspects of the invention.Various changes may be made to the invention described and equivalentsmay be substituted without departing from the spirit and scope of theinvention.

For example, while advantageously utilized with AR displays that provideimages across multiple depth planes, the virtual content disclosedherein may also be displayed by systems that provide images on a singledepth plane.

In addition, many modifications may be made to adapt a particularsituation, material, composition of matter, process, process act, orstep(s) to the objective(s), spirit, or scope of the present invention.Further, as will be appreciated by those with skill in the art that eachof the individual variations described and illustrated herein hasdiscrete components and features which may be readily separated from orcombined with the features of any of the other several embodimentswithout departing from the scope or spirit of the present inventions.All such modifications are intended to be within the scope of claimsassociated with this disclosure.

The invention includes methods that may be performed using the subjectdevices. The methods may comprise the act of providing such a suitabledevice. Such provision may be performed by the user. In other words, the“providing” act merely requires the user obtain, access, approach,position, set-up, activate, power-up or otherwise act to provide therequisite device in the subject method. Methods recited herein may becarried out in any order of the recited events that is logicallypossible, as well as in the recited order of events.

In addition, it will be appreciated that each of the processes, methods,and algorithms described herein and/or depicted in the figures may beembodied in, and fully or partially automated by, code modules executedby one or more physical computing systems, hardware computer processors,application-specific circuitry, and/or electronic hardware configured toexecute specific and particular computer instructions. For example,computing systems may include general purpose computers (e.g., servers)programmed with specific computer instructions or special purposecomputers, special purpose circuitry, and so forth. A code module may becompiled and linked into an executable program, installed in a dynamiclink library, or may be written in an interpreted programming language.In some embodiments, particular operations and methods may be performedby circuitry that is specific to a given function.

Further, certain embodiments of the functionality of the presentdisclosure are sufficiently mathematically, computationally, ortechnically complex that application-specific hardware or one or morephysical computing devices (utilizing appropriate specialized executableinstructions) may be necessary to perform the functionality, forexample, due to the volume or complexity of the calculations involved orto provide results substantially in real-time. For example, a video mayinclude many frames, with each frame having millions of pixels, andspecifically programmed computer hardware is necessary to process thevideo data to provide a desired image processing task or application ina commercially reasonable amount of time.

Code modules or any type of data may be stored on any type ofnon-transitory computer-readable medium, such as physical computerstorage including hard drives, solid state memory, random access memory(RAM), read only memory (ROM), optical disc, volatile or non-volatilestorage, combinations of the same and/or the like. In some embodiments,the non-transitory computer-readable medium may be part of one or moreof the local processing and data module (140), the remote processingmodule (150), and remote data repository (160). The methods and modules(or data) may also be transmitted as generated data signals (e.g., aspart of a carrier wave or other analog or digital propagated signal) ona variety of computer-readable transmission mediums, includingwireless-based and wired/cable-based mediums, and may take a variety offorms (e.g., as part of a single or multiplexed analog signal, or asmultiple discrete digital packets or frames). The results of thedisclosed processes or process steps may be stored, persistently orotherwise, in any type of non-transitory, tangible computer storage ormay be communicated via a computer-readable transmission medium.

Any processes, blocks, states, steps, or functionalities describedherein and/or depicted in the attached figures should be understood aspotentially representing code modules, segments, or portions of codewhich include one or more executable instructions for implementingspecific functions (e.g., logical or arithmetical) or steps in theprocess. The various processes, blocks, states, steps, orfunctionalities may be combined, rearranged, added to, deleted from,modified, or otherwise changed from the illustrative examples providedherein. In some embodiments, additional or different computing systemsor code modules may perform some or all of the functionalities describedherein. The methods and processes described herein are also not limitedto any particular sequence, and the blocks, steps, or states relatingthereto may be performed in other sequences that are appropriate, forexample, in serial, in parallel, or in some other manner. Tasks orevents may be added to or removed from the disclosed exampleembodiments. Moreover, the separation of various system components inthe embodiments described herein is for illustrative purposes and shouldnot be understood as requiring such separation in all embodiments. Itshould be understood that the described program components, methods, andsystems may generally be integrated together in a single computerproduct or packaged into multiple computer products.

Example aspects of the invention, together with details regardingmaterial selection and manufacture have been set forth above. As forother details of the present invention, these may be appreciated inconnection with the above-referenced patents and publications as well asgenerally known or appreciated by those with skill in the art. The samemay hold true with respect to method-based aspects of the invention interms of additional acts as commonly or logically employed.

In addition, though the invention has been described in reference toseveral examples optionally incorporating various features, theinvention is not to be limited to that which is described or indicatedas contemplated with respect to each variation of the invention. Variouschanges may be made to the invention described and equivalents (whetherrecited herein or not included for the sake of some brevity) may besubstituted without departing from the spirit and scope of theinvention. In addition, where a range of values is provided, it isunderstood that every intervening value, between the upper and lowerlimit of that range and any other stated or intervening value in thatstated range, is encompassed within the invention.

Also, it is contemplated that any optional feature of the inventivevariations described may be set forth and claimed independently, or incombination with any one or more of the features described herein.Reference to a singular item, includes the possibility that there areplural of the same items present. More specifically, as used herein andin claims associated hereto, the singular forms “a,” “an,” “said,” and“the” include plural referents unless the specifically stated otherwise.In other words, use of the articles allow for “at least one” of thesubject item in the description above as well as claims associated withthis disclosure. It is further noted that such claims may be drafted toexclude any optional element. As such, this statement is intended toserve as antecedent basis for use of such exclusive terminology as“solely,” “only” and the like in connection with the recitation of claimelements, or use of a “negative” limitation. Without the use of suchexclusive terminology, the term “comprising” in claims associated withthis disclosure shall allow for the inclusion of any additionalelement—irrespective of whether a given number of elements areenumerated in such claims, or the addition of a feature could beregarded as transforming the nature of an element set forth in suchclaims.

Accordingly, the claims are not intended to be limited to theembodiments shown herein, but are to be accorded the widest scopeconsistent with this disclosure, the principles and the novel featuresdisclosed herein.

What is claimed is:
 1. A method implemented by a head-mounted display system having one or more processors, the method comprising: providing a rendered frame of virtual content, the rendered frame comprising at least a portion associated with a second resolution; causing an emissive micro-display projector to output light forming a first subframe of the rendered frame, the first subframe having a first resolution less than the second resolution; wherein the emissive micro-display projector comprises an array of light emitters associated with the first resolution and having a pixel pitch; after causing the emissive micro-display projector to output light forming the first subframe of the rendered frame, shifting, via one or more actuators; one or more parts of the emissive micro-display projector to adjust geometric positions associated with light output by the emissive micro-display projector; wherein the geometric positions are adjusted a distance less than the pixel pitch; and after shifting the one or more parts of the emissive micro-display projector, causing the emissive micro-display projector to output light forming a second subframe of the rendered frame, the second subframe having the first resolution.
 2. The method of claim 1, wherein the portion associated with the second resolution is associated with a foveal region of a user's eye.
 3. The method of claim 2, further comprising: determining that light forming the portion associated with the second resolution falls within a threshold angular distance of a fovea of the user.
 4. The method of claim 2, further comprising: for the second subframe, causing light emitters to update emitted light forming the portion associated with the second resolution; and for the first subframe, causing light emitters to not update emitted light forming parts of the rendered frame outside of the portion associated with the second resolution.
 5. The method of claim 1, wherein a total number of subframes of the rendered frame is determined based on a size associated with the pixel pitch and an emitter size.
 6. The method of claim 5, further comprising: causing the emissive micro-display projector to successively output light forming the total number of subframes.
 7. The method of claim 6, further comprising: time multiplexing the rendered frame by causing the one or more actuators to shift the one or more parts of the emissive micro-display projector for each subframe.
 8. The method of claim 7, wherein causing the one or more actuators to shift the one or more parts of the emissive micro-display projector for each subframe includes causing the one or more actuators to shift the one or more parts of the emissive micro-display projector such that geometric positions associated with the array of light emitters are tiled within respective inter-emitter regions.
 9. The method of claim 1, wherein causing the one or more actuators to shift the one or more parts of the emissive micro-display projector includes causing the one or more actuators to shift the one or more parts of the emissive micro-display projector according to a continual movement pattern.
 10. The method of claim 1, wherein causing the one or more actuators to shift the one or more parts of the emissive micro-display projector includes causing the one or more actuators to shift the array of light emitters of the emissive micro-display projector along one or more axes.
 11. The method of claim 1, wherein causing the one or more actuators to shift the one or more parts of the emissive micro-display projector includes causing the one or more actuators to shift projection optics of the emissive micro-display projector along one or more axes, the projection optics being configured to output light to a user of the head-mounted display system.
 12. A system, comprising: an emissive micro-display projector system; one or more processors; and one or more computer storage media storing instructions that, when executed by the one or more processors, cause the one or more processors to perform operations comprising: generating a rendered frame of virtual content to be displayed as augmented reality content via the emissive micro-display projector system, the rendered frame being associated with a second resolution, and the emissive micro-display projector system comprising one or more light emitter arrays configured to output light forming virtual content associated with a first, lower, resolution; dividing the rendered frame of virtual content into a plurality of subframes, wherein each subframe includes a subset of pixels included in the rendered frame; and successively outputting light via the emissive micro-display projector system, the light forming the plurality of subframes, wherein one or more parts of the emissive micro-display projector system is shifted via one or more actuators for each of the subframes according to a movement pattern, wherein the one or more parts of the emissive micro-display projector system is shifted along one or more axes on a plane parallel to a plane of an output pupil of the emissive micro-display projector system.
 13. The system of claim 12, wherein the one or more processors are configured to cause the one or more actuators to shift the one or more parts of the emissive micro-display projector system such that geometric positions associated with the light emitter arrays are tiled within respective inter-emitter regions.
 14. The system of claim 12, wherein the one or more processors are configured to cause the one or more actuators to shift the light emitter arrays of the emissive micro-display projector system along the one or more axes.
 15. The system of claim 12, wherein the emissive micro-display projector system comprises projection optics, and wherein the one or more processors are configured to cause the one or more actuators to shift the projection optics along the one or more axes, the projection optics being configured to output light to a user of the system.
 16. A method implemented by a head-mounted display system of one or more processors, the method comprising: generating a rendered frame of virtual content to be displayed as virtual content via an emissive micro-display projector system of the head-mounted display system, the rendered frame being associated with a second resolution, and the emissive micro-display projector system comprising light emitters configured to output light forming virtual content associated with a first, lower, resolution; dividing the rendered frame of virtual content into a plurality of subframes, wherein each subframe includes a subset of pixels included in the rendered frame; and successively outputting light via the emissive micro-display projector system, the light forming the plurality of subframes, wherein one or more parts of the emissive micro-display projector system is shifted along one or more axes via one or more actuators for each of the subframes according to a movement pattern, wherein the one or more parts of the emissive micro-display projector system is shifted along one or more axes on a plane parallel to a plane of an output pupil of the emissive micro-display projector system.
 17. The method of claim 16, wherein the emissive micro-display projector system is shifted such that geometric positions associated with the light emitters of the missive micro-display projector system are tiled within respective inter-emitter regions.
 18. The method of claim 16, wherein the one or more actuators shift the light emitters of the emissive micro-display projector system along the one or more axes.
 19. The method of claim 16, wherein the one or more actuators shift projection optics of the emissive micro-display projector system along the one or more axes, the projection optics being configured to output light to a user of the head-mounted display system. 